耶鲁大学博弈论公开课 - 第2集 沉默，信令和苦难教育

视频全文转录（中英双语）

以下为完整中英双语转录，已加标点。英文在前，中文在后，逐段对照。

由 Groq Whisper 转录 → M2.7 B 方案整文标点 + 分段 → M2.7 段号保留翻译 → 逐段对照。

[段 1]

Okay, so today we’re going to study asymmetric information, it’s our last week, and we’re going to focus on signaling today, and I’ll spell it with one L here as a concessions to the Americans. All right, so we’re going to divide this class into two parts, and for the first part, we’re going to focus on the case where there is some verifiable, verifiable information. in the problem. Alright, so we’ll see what this means in a while, but let me just set up an example and we’ll see where that takes us. So I want to return to a game we know well by this stage, which is the Cournot game. So there’s two firms, and they’re competing in Cournot, so they’re competing in quantities. And we’ll call the firms A and B. And suppose that firm B has costs so to be more formal these are constant marginal costs are equal to Cm where m means middle or medium or something and firm A firm A also has costs but those costs could come in one of three types it could be that firm A has high costs and high costs are equal to middle costs plus a little bit. And it could be that firm A also has medium costs, and it could be that firm A has low costs. And the low costs are just the medium costs minus a little bit.

[译文 1]

好的，今天我们要学习不对称信息，这是我们最后一周的内容，今天我们将聚焦于信号传递，我把它拼写成只有一个L，向美国人表示一点让步。好，我们把这节课分成两部分，在第一部分中，我们要关注的是存在某种可验证信息的情况。好，我们稍后会看到这个是什么意思，让我先举一个例子，看看会把我们带向何方。我想回到我们已经很熟悉的一个博弈，那就是古诺博弈。有两家企业，它们在古诺竞争中展开竞争，即在产量上进行竞争。我们称这两家企业为A和B。假设企业B的成本，用更正式的方式说，这些是常数边际成本，等于Cm，其中m表示中等或中位数的意思，企业A，企业A也有成本，但这些成本可能有三种类型，可能是企业A有高成本，高成本等于中等成本加上一点。也可能是企业A有中等成本，还可能是企业A有低成本。低成本就是中等成本减去一点。

[段 2]

Now before this competition is going to take place, before they’re actually going to play the Cournot game, firm A has an opportunity. Firm A’s opportunity is to reveal its costs to Firm B. Just to make this more explicit, initially Firm B obviously knows his own costs, and since there is only one type, Firm A obviously knows those costs as well. So Firm A and Firm B know what Firm B’s costs are. But initially, although Firm A knows her own costs, Firm B does not know Firm A’s costs. All right, let’s write that up. So firm B knows only its costs, and firm A knows both costs. but the key decision we’re going to focus on is that firm A has an opportunity to reveal its true costs to firm B. Now it can do so in a verifiable way. For example, it could hire an accountant. That accountant from a reputable outside firm could come in and do the accounts for firm A and then publish them in the Wall Street Journal or something. So firm A can do that and let’s assume it’s costless for it to do that. So Fermi can costlessly and verifiably verifiably reveal its costs to B. And the question is, this is going to happen before they play Cournot, the question is should Firm A reveal those costs or not?

[译文 2]

现在，在这场竞争即将发生之前，在它们实际进行古诺博弈之前，企业A有一个机会。企业A的机会是向企业B披露其成本。为了让这更明确，最初企业B显然知道自己的成本，而且由于只有一种类型，企业A显然也知道这些成本。因此企业A和企业B都知道企业B的成本是多少。但最初，虽然企业A知道自己 的成本，企业B却不知道企业A的成本。好，让我们把它写下来。所以企业B只知道自己的成本，而企业A知道两个成本。但我们要关注的关键决策是企业A有机会向企业B披露其真实成本。现在它可以用可验证的方式做到这一点。例如，它可以聘请一位会计师。那位来自信誉良好的外部公司的会计师可以进来为企业A做账，然后发表在《华尔街日报》上或类似的地方。所以企业A可以做到这一点，让我们假设它做这件事是没有成本的。因此费米可以无成本地且可验证地向B披露其成本。问题是，这会发生在它们进行古诺博弈之前，问题是企业A应该披露这些成本还是不应该？

[段 3]

Should Firm A publicize and give away its informational advantage, if you like, to Firm B by telling Firm B what its costs look like. So what do people think? Let me just grab the mic and ask people a little bit. Imagine you’re the manager of Firm A. Are you going to tell Firm B what your costs are or not? Do you want to wave a hand on the air or should I just cold call here? Let me cold call. So what’s your name, sir? You. You and and and and so suppose you’re the manager of Firm A. Would you reveal the information or not?firm A, would you reveal the information or not? I would tell them only if my costs were lower. All right. So you says, I would reveal the information only if my costs were lower. Now, why do you want to reveal the costs if you have lower costs? Because then my firms will produce at a lower cost, so firm B will produce less because they know that we’ll get most of the market. Good, good. So the point that you is making is, there may be some advantage in having the other side know my costs if my costs are low, since that may induce the other side to produce less. Let’s just fill out that argument by putting in the Cournot diagram.

[译文 3]

企业A是否应该公布并放弃其信息优势，如果你愿意这么理解的话，通过告诉企业B其成本状况来给予企业B。大家都怎么想？让我拿起麦克风稍微问一下大家。假设你是企业A的经理。你打算告诉企业B你的成本是多少还是不告诉？我要在空中举手还是直接点名？让我点名吧。你叫什么名字，先生？你。假设你是企业A的经理。你会披露信息还是不披露？企业A，你会披露信息还是不披露？只有当我的成本更低时我才会告诉他们。好，你说，你说我只有当成本更低时才会披露信息。现在，为什么当成本更低时你想披露成本？因为那样我的企业将以更低的成本生产，因此企业B会生产更少，因为它们知道我们将获得大部分市场份额。好的，好的。所以你提出的观点是，当我的成本较低时，让对方知道我的成本可能有一些优势，因为这可能会促使对方减少生产。让我们通过放入古诺图来详细阐述这个论点。

[段 4]

So here’s the Cournot diagram. Here’s the quantity for firm A. Here’s the quantity for firm B. And here is the best response or reaction curve for firm B. And in this picture, there’s going to be three different possible reaction curves for firm A, each one corresponding to different costs. So, for example, this could be the reaction curve or the best response for firm A in the case in which it’s medium. But if it had lower costs, what would happen to that reaction curve? Would it shift in? Would it tilt? What would happen to it? Someone shout it out? It would shift out. Or if it had lower costs, then it would shift out. So this would be the best response for first.it would shift out, so this would be the best response for firm A in the low case, and conversely, this would be the best response for firm A in the high case. So the point that Yu is making, or he should correct me if this is unfairly paraphrasing him, is if I have low costs, then I want the other side to know I have low costs, because that puts us into the equilibrium in which this is my best response curve, and this is the other side’s best response curve, and firm B ends up producing less, ends up lowering its production.

[译文 4]

这是古诺图。这是企业A的产量。这是企业B的产量。这是企业B的最佳反应或反应曲线。在这张图中，将有三条不同的可能反应曲线对应于企业A，每条对应不同的成本。例如，这可能是企业A在其为中等成本情况下的反应曲线或最佳反应。但如果它的成本更低，那条反应曲线会发生什么变化？会向内移动吗？会倾斜吗？会发生什么？有人喊出来吗？会向外移动。或者如果成本更低，它会向外移动。所以这将是企业A在低成本情况下的最佳反应曲线，相反，这将是企业A在高成本情况下的最佳反应曲线。所以你提出的观点，或者如果我概括得不公平请纠正我，是如果我有低成本，我希望另一方知道我 有低成本，因为这把我们带入一个均衡，这是我 的最佳反应曲线，这是另一方的最佳反应曲线，而企业B最终会生产更少，会降低其产量。

[段 5]

Is that right? So the key idea here is that this is a game, an idea we’ve had often, this is a game of strategic substitutes. So if I have low costs, I want the other side to know that I have low costs, because it will cut back its production, which helps me. All right. On the other hand, if I have high costs, if I have high costs, then I’d kind of like to remain hidden. I really don’t want the other side to know that I have high costs. All right. Because if I have high costs, then the other firm is actually going to increase their production and that’s going to hurt me. All right. But notice I’ve twisted the question a little bit. The question I actually asked you was, would you reveal the information about your costs? And I flipped that around to a slightly easier question, which is, what wouldto a slightly easier question, which is, what would I like the other side to know? All right? Now, what would I like the other side to know? I’d like the other side to know if I have low costs. I’d like the other side not to know if I have high costs. But that’s not quite the question we asked. The question we asked was, would you, given whatever your costs are, reveal that information to the other side?

[译文 5]

是这样吗？这里的关键概念是这是一个博弈，一个我们经常遇到的概念，这是一个战略替代品的博弈。所以如果我有低成本，我希望另一方知道我 有低成本，因为这会促使它削减产量，这对我有帮助。好。另一方面，如果我有高成本，如果我有高成本，那我宁愿隐藏起来。我真的不希望对方知道我 有高成本。因为如果我有高成本，那么另一家企业实际上会 增加它们的产量，而这会对我不利。好。但请注意我把问题稍微扭曲了一下。我实际问你们的问题是，你会披露关于你成本的信息吗？我把它转 换成了一个稍微微容易一点的问题，那就是，我希望对方知道什么？好，我希望对方知道什么？我希望对方知道我 有低成本。我不希望对方知道我 有高成本。但这不完全是我们问的问题。我们问的问题是，鉴于你的成本是多少，你会向对方披露那个信息吗？

[段 6]

And I think what you has told us is, to say exactly what you said if you said if I had low costs I’m going to reveal it to the other side is that right all right so far what do we know so far we know that if I have low costs then I will reveal it all right so far we know that but what if I don’t have low costs? What if I have middling costs or high costs? Well let’s take these in turn what about middling costs? What should I do if I have middle level costs? Alright, so somebody’s got their hand up let me go and take advantage of that, hang on I’ll come back What’s your name? Shout out Alec Alec I think you should still reveal because they know if you had low cost you would reveal and so if you had umyou would reveal. And so if you had middle costs and you didn’t reveal, then they could think that you either had middle costs or high costs, and it’s better for you to just reveal that you had middle costs. Good, good. Do people hear that? Let’s repeat that, all right? So you might think, you might think that if I have middle costs, you might think that I could reveal or not reveal, depending on what the other side thought.

[译文 6]

我认为你告诉我们的正是，你说的正是你说的，如果你说如果我成本低我就向对方披露，是这样吗，到目前为止我们都同意，到目前为止我们知道如果我有低成本我就会披露，好，到目前为止我们知道这一点，但如果我没有低成本呢？如果我有中等成本或高成本呢？让我们依次来看，中等成本怎么办？如果我有中等成本我应该怎么做？好，有人举手了让我利用这个机会，等一下我会回来，你叫什么名字？大声说出来，亚历克。亚历克，我认为你还是应该披露，因为它们知道如果你有低成本你会披露，所以如果你有你 会披露。所以如果你有中等成本而你不披露，那么它们会认为你可能是中等成本或高成本，而你最好是直接披露你有中等成本。好的，好的。大家听到这个观点了吗？让我们重复一下，好？所以你可能会认为，你可能会认为如果我有中等成本，你可能会认为我可以披露也可以不披露，取决于对方怎么想。

[段 7]

However, what Alex is arguing, correctly, is if I don’t reveal that I have middle costs, the other side, firm B, knows that my costs are not low. The only way they could mistake me is they could think I’m a high-cost firm. They know I’m not a low-cost firm. How do they know I’m not a low-cost firm? Because the low-cost firm would have revealed that was you’s argument. Since low-cost firms are revealing, if I’m a middle-cost firm, If I don’t reveal, no one’s in any doubt I’m not a low-cost firm. So all I could be is a middle-cost firm or a high-cost firm. All I could have is this reaction curve, which is the one I actually have, or this reaction curve. So if I don’t reveal, then the other side might think that I have high costs, in which case they’re actually going to increase their production and hurt me. Hang on a second. all right so since since the low-cost firm is going to reveal the medium cost wants tocost firm is going to reveal the medium cost wants to reveal to ensure that no one thinks it’s high cost all right so that so low cost reveals and therefore therefore CM reveals as well to prevent prevent being mistaken for a a high-cost firm. Now there was a question, let me come down and collect the question.

[译文 7]

然而，亚历克斯正确地指出，如果我不透露我拥有中等成本，另一方即B公司，就会知道我的成本不是低的。他们唯一可能误解我的方式是认为我是一家高成本公司。他们知道我并非低成本公司。为什么他们确定我不是低成本公司？因为低成本公司本来就会透露——这是你们的论点。既然低成本公司会透露，如果我是一家中等成本公司，如果我不透露，没有人会怀疑我不是低成本公司。所以我可能只是一家中等成本公司或高成本公司。我可能只有这条反应曲线，也就是我实际拥有的那条，或这条反应曲线。因此，如果我不透露，另一方可能会认为我拥有高成本，在这种情况下他们实际上会增加产量并损害我。等一下。好的，既然低成本公司会透露，中等成本公司也想要透露，以确保没有人认为它是高成本，所以低成本会透露，因此中等成本也会透露，以防止被误认为是高成本公司。现在有个问题，让我下来收集这个问题。

[段 8]

Yeah? I was just going to ask, what if you have a reveal for both the low and middle cost, then they’re obviously going to know it’s a high cost, which means that the concealing doesn’t do any good. Exactly. Exactly. And your name is? Bethany. So Bethany’s pointing out that once we know the low-cost type’s going to reveal, we know that the middle-cost type is also going to reveal, so as not to get mistaken for being high cost, which means if you’re running a high cost firm, it really doesn’t matter whether you reveal or not, because you’re going to be revealed by the fact that you didn’t reveal. Is that right? Right? Had you been low cost, you would have revealed. Had you been middle cost, you would have revealed. And therefore, whether you choose to reveal or not, everyone knows that you’re high cost. So therefore, CH is revealed. is revealed. Everyone see that? Alright. Okay. Now notice that in this argument we’ve just constructed, there were three types of firm. High, middle, low. But I could have constructed exactly the same argument, albeit somewhat more tediously, with a hundred types of firms. Firms that had absolutely the lowest cost, firms that had the 99th highest cost, 98th highest cost, 97th highest cost, and so on, and this argument would have been exactly the same.

[译文 8]

是吗？我正想问，如果你同时透露低成本和中等成本，那他们明显会知道这是高成本，这意味着隐瞒没有任何好处。确实如此。确实如此。你叫什么名字？贝萨尼。所以贝萨尼指出，一旦我们知道低成本类型会透露，我们就知道中等成本类型也会透露，以免被误认为高成本，这意味着如果你经营一家高成本公司，你是否透露实际上无关紧要，因为你会因为你没有透露而被揭露。就是这样吗？是的？如果你成本低，你就会透露。如果你成本中等，你就会透露。因此，无论你选择透露与否，每个人都知道你是高成本。所以，高成本公司会被揭露。每个人看到了吗？好的。好的。现在注意，在我们刚刚构建的这个论点中，有三种类型的公司：高成本、中等成本、低成本。但我可以用一百种类型的公司来构建完全相同的论点，尽管会更繁琐一些：公司具有绝对最低成本、第99高成本、第98高成本、第97高成本，以此类推，这个论点会完全相同。

[段 9]

At each stage, the firm that’s left in the analysis who has the lowest cost will want to reveal to distinguish itself from those who haven’t revealed, quote, yet, unquote, and therefore will get unraveling and will get information to be revealed. And notice, interestingly, we’ll get information to be revealed beyond the median. So the 51st highest cost firm will reveal, therefore the 50th highest cost firm will reveal, therefore the 49th and so on. In fact, the only firm who won’t explicitly actively reveal themselves is the firm who has absolutely the highest cost, and as Bethany points out, they’re going to be revealed anyway. All right? So this is an idea, this idea is called informational unraveling. And again, in keeping from my American audience, I’m going to put one L in unraveling.audience I’m going to put one L in unraveling. Is that right? There’s one L in America, right? Someone should just check that on Google or something. I think that’s great. All right. All right. What’s the lesson here? So one lesson is that this happens. We’ll come back to that. But another lesson, perhaps a more important lesson, is often the lack of information, the lack of somebody signaling to you, the lack of somebody trying to tell you something conveys information. This was the point that Bethany was making. The fact that the high-cost firm doesn’t, in fact, go out and reveal information to you reveals something about what it knows.

[译文 9]

在每个阶段，留在分析中的具有最低成本的公司会想要透露，以将自己与那些尚未透露的人区分开来，因此会产生信息瓦解，并且会获得被透露的信息。有趣的是，我们会获得超越中位数的被透露信息。因此，第51高成本公司会透露，因此第50高成本公司会透露，因此第49个，以此类推。事实上，唯一不会明确主动透露自己的公司是具有绝对最高成本的公司，正如贝萨尼指出的那样，他们无论如何都会被揭露。对吧？所以这个想法被称为信息瓦解。同样，为了我的美国听众，我将把一个L放在unraveling中。对吧？在美国有一个L，对吧？有人应该在Google上检查一下。我觉得这很棒。好的。好的。这里的教训是什么？所以一个教训是这会发生。我们会回到这一点。但另一个教训，也许更重要的教训是，经常缺乏信息、缺乏某人向你发出信号、缺乏某人试图告诉你某事传达了信息。这正是贝萨尼提出的观点。事实上，高成本公司不主动向你透露信息这一事实，揭示了它所知道的一些信息。

[段 10]

So Yu’s initial comment was correct. If I was the high-cost firm, I’d like to remain hidden, but I can’t remain hidden. From your point of view as the receiver of the information, there’s information in the lack of the attempt to convey information. So in lesson, the lack of a signal the lack of an attempt to affirm to signal use of information the lack of a signal can be informative. So this is an often forgotten lesson. It’s a very simple idea but there’s a natural tendency when you’re dealing with information to focus on the evidence that is there rather than the evidence that’s not there. Alright? There’s an expression that goesalright there’s an expression that goes with this the expression is silence speaks volumes alright you’ve all heard that expression silence speaks volumes let me give you one other example there’s a Sherlock Holmes story by the way do you all know who Sherlock Holmes is yeah good ok so there’s a Sherlock Holmes story in which Sherlock Holmes solves the murder he figures out who did the murder and Dr.

[译文 10]

所以余最初的评论是正确的。如果我是高成本公司，我愿意保持隐藏，但我无法保持隐藏。从你作为信息接收者的角度来看，在缺乏尝试传达信息的过程中存在信息。所以在教训中，缺乏信号、缺乏确认信号的尝试、使用信息的缺乏信号可以提供信息。所以这是一个经常被遗忘的教训。这是一个非常简单的想法，但当你处理信息时，有一种自然倾向，即专注于存在的证据而不是不存在的证据。对吧？有句话伴随着这个，这句话是沉默胜千言，对吧？你们都听过这句话，沉默胜千言，让我给你们另一个例子，顺便说一句，有一个夏洛克·福尔摩斯的故事，你们都知道夏洛克·福尔摩斯是谁，对吧？好的，所以有一个夏洛克·福尔摩斯的故事，夏洛克·福尔摩斯解决了谋杀案，他

[段 11]

Watson who’s his sidekick is trying to figure out how Holmes could possibly have solve the murder and he says how did you solve the murder and Holmes says it’s because of the it’s because of the barking dog all right and Watson says what do you mean it’s because the barking dog the dog didn’t bark right and Holmes says that’s exactly the point the fact that the dog didn’t bark didn’t make any sound tells us who must have committed the murder right it’s very easy to fall into the trap of being Watson and to ignore the thing that didn’t happen and focus on the things that did happen so here it’s easy to forget that actually the high-cost firm is revealed by doing nothing. All right, this is the idea that silence can speak volumes. Every year I go back and try and figure out what that quotation is from and I can never find it. So when anybody finds it I will give them a prize of some sort. Originally I thought it must be Shakespeare but it doesn’t appear to be. All right.

[译文 11]

华生，他的助手，正试图弄清楚Holmes是如何解决这起谋杀案的，他问你是如何解决这起谋杀案的，Holmes说是因为狗叫声。好的，华生说你是说因为狗叫声？狗没有叫，对吧？Holmes说那正是关键，狗没有叫这一事实告诉我们一定是某人犯了谋杀罪。是的，很容易陷入华生的陷阱，忽略没有发生的事情，专注于发生的事情。所以这里很容易忘记，实际上高成本公司通过什么都不做就被揭露了。对吧，这就是沉默胜千言的道理。我每年都回去试图找出这句话的出处，但我永远找不到。所以当任何人找到它时，我会给他们某种奖励。起初我以为一定是莎士比亚，但它似乎不是。好的。

[段 12]

So this is a little example involving Cournot, but I want to try and convinceinvolving Cournot but I want to try and convince you and I’m trying to convince you this example is more generalist but let’s pick up the question yeah sorry go ahead an equilibrium where it’s the cost of remaining hidden as a middle cost firm outweighs the benefit I mean outweighs not not not not not not if we take the model literally we take the model in corner literally because if you if suppose the firm B doesn’t know whether you’re high or middle, then he’s going to think your cost is somewhere in between, and relative to your cost being middle, he’s going to produce more. That’s the point here. Now, it’s true that in a richer model, there may be some other advantage in having information hidden, but that would have already applied to the low-cost firm. Let me give you some other examples, and we’ll see this in other contexts and see that it might actually ring true. So one other example involves resumes. All right, so this example requires some explanation for the non-Americans. How many of you are non-Americans here? All right, so one thing you need to know as non-Americans is the way in which people write resumes in America. You all know what a resume is, right? A CV or resume, right?

[译文 12]

这是一个涉及古诺的小例子，但我想说服你，这个例子更具有普遍性。让我们继续这个问题。是的，抱歉，请继续。作为一家中等成本公司，保持隐藏的成本超过收益的均衡。我是说，如果从字面上理解这个模型，因为如果你假设B公司不知道你是高成本还是中等成本，那么他会认为你的成本介于两者之间，与你的成本是中等成本相比，他会生产更多。这就是这里的要点。现在，在更丰富的模型中，隐藏信息可能确实有一些其他优势，但那只适用于低成本公司。让我给你们一些其他例子，我们会在其他背景中看到这一点，看到它可能确实真实。另一个例子涉及简历。是的，所以这个例子需要为非美国人做一些解释。你们中有多少是非美国人？好的，作为非美国人，你需要了解的是美国人写简历的方式。你们都知道什么是简历，对吧？简历或简历，对吧？

[段 13]

So when you look at a typical resume from an American student, if you’re not American, for those of you who aren’t American, how should I put this politely? It has a tendency to make you want to vomit. Is that it? Yeah, okay. So that’s basically the polite version of what I was going to say about that. All right. So why does it have a tendency to make you want to vomit? Because Americans,Why does it have a tendency to make you want to vomit? Because Americans have a tendency to put down everything on their resume. So if they were captain of the chess team in third grade, and there they are now, they’re 40 and applying for a job, it still says, I was captain of the chess team in third grade. And this is particularly true when it comes to public service, when it comes to sort of moral acts. So most people in Europe will be a bit embarrassed about writing their good deeds on their resumes, but Americans, there’s a little spot on their resume which is about their good deeds or their public service, and they put everything. You know, when I was eight, I helped a little old lady across the road with her shopping basket, and there it is on their resume, right? So why? Why is it that Americans reveal so much information on their resume?

[译文 13]

所以当你看一份典型的美国学生简历时，如果你们不是美国人，对于那些不是美国人的人，我该怎么委婉地说呢？它往往会让你想吐。是这样吗？是的，好吧。所以这基本上就是我要说的那个版本的委婉说法。好吧。那么为什么它往往会让你想吐呢？因为美国人，为什么它往往会让你想吐呢？因为美国人倾向于在简历上写所有的东西。所以如果他们在三年级时是象棋队的队长，而现在他们40岁正在申请一份工作，简历上仍然写着，我在三年级时是象棋队的队长。这种情况在公共服务方面特别真实，在道德行为方面也是如此。所以大多数欧洲人会不好意思在简历上写他们的善行，但美国人，简历上有一小块地方是关于他们的善行或公共服务的，他们把所有东西都写上去。你知道的，当我八岁的时候，我帮助一位老太太过马路，手里拿着购物篮，而这件事就写在他们的简历上，对吧？那么为什么？为什么美国人在简历上透露这么多信息？

[段 14]

Well, think about informational unraveling, right? So resumes are verifiable information. It’s hugely costly to be caught cheating about your resume, so basically you’re not going to lie on your resume, all right? And imagine if I’m admitting students, let’s say, to law school, to Yale Law School, and I’m reading the student’s resume, and in the spot where I’m expecting to see public service, there’s nothing written there. What do I assume about that student? What do I assume about that student? I assume that the person did nothing. This person has been a self-serving evil git their entire life, has never even helped a little old lady across the road. All right? So people put down everything, even these minimal things, even these pretty shockingly tiny accessories,pretty shockingly tiny acts of charity to reveal themselves from those people who did absolutely nothing that are basically the devil incarnate. Alright? Alright? Alright? So this is about resumes. Let’s take this a bit further. How many of you are from Los Angeles? Alright, so in Los Angeles I’m led to, I’m told, you can confirm this or not, there are lots and lots of restaurants. This is true, right? Lots of restaurants. And some of these restaurants are good and some of them are bad and more to the point for today’s example, some of these restaurants are clean and some of them are not so clean.

[译文 14]

好吧，想想信息泄露，对吧？所以简历是可验证的信息。被发现在简历上作弊的代价非常高，所以基本上你不会在简历上撒谎，好吗？想象一下如果我在录取学生，比如说，录取到法学院，耶鲁法学院，我在读学生的简历，在我期望看到公共服务的那个地方，那里什么都没写。我会假设这个学生什么？我会假设这个学生什么？我假设这个人什么都没做。这个人一辈子都是自私自利的混蛋，从来没有帮助过一位老太太过马路，好吗？所以人们写上所有的东西，甚至这些最小的事情，甚至这些非常令人震惊的微小的善举，来将自己与那些什么都没做的人区分开来，那些人基本上就是恶魔的化身。好吗？好吗？好吗？所以这是关于简历的。让我们把这个进一步延伸。你们中有多少人是来自洛杉矶的？好吧，在洛杉矶，我被告知，你们可以确认或不确定，有很多很多餐厅。这是真的，对吧？很多餐厅。其中一些餐厅很好，有一些很差，更重要的是对于今天的例子，其中一些餐厅很干净，有一些不太干净。

[段 15]

Right, is this true? Is this true? Yeah? Okay, so it turns out that until the late 90s the Los Angeles Municipality rules, local law, said that every restaurant in Los Angeles County, I think it was, had to get visited by the health inspector. And the health inspector would come around, I think it was annually, and go to these restaurants and they would issue a certificate. And this was a health certificate and written on it in large letters, I think they were red letters, was either A or B or C. It may even have been A minuses as well, but for the purpose of the story, let’s just call it A, B, and C. Now, that was all the law said. The law did not say that you had to display your health certificate anywhere. So what does this model tell us to expect about Los Angeles in the mid-90s? well if you have if you’re running a little restaurant in Los Angeles and youyou’re running a little restaurant in Los Angeles and you get an A health certificate from your restaurant, from the health inspector, what are you going to do with that A certificate? You’re going to display it prominently in the window, right? A health certificate. All right? So if you’re running a slightly less healthy restaurant, maybe this is Ale’s pizza chain again, all right?

[译文 15]

对，这是真的吗？这是真的吗？是的？好吧，所以直到90年代末，洛杉矶市政府的规定，当地的法律，说洛杉矶县的每一家餐厅，我想是这样的，必须接受健康检查员的访问。健康检查员会来，我想是每年一次，去这些餐厅，他们会颁发证书。这是一张健康证书，上面用大字写着，我想是用红字写的，是A、B或C。它可能也有A减，但为了故事的目的，我们姑且称之为A、B和C。现在，这就是法律所说的全部。法律没有说你必须在任何地方展示你的健康证书。那么这个模型告诉我们对90年代中期的洛杉矶有什么期望呢？好吧，如果你在洛杉矶经营一家小餐厅，你在洛杉矶经营一家小餐厅，你从健康检查员那里得到了A健康证书，从你的餐厅，从健康检查员那里，你会怎么处理那张A证书？你会把它们突出地展示在橱窗里，对吧？一张健康证书。好吧？所以如果你经营的是一家健康程度稍低的餐厅，也许这是Ale的披萨连锁店，再次，好吗？

[段 16]

And you still get a B certificate from the Los Angeles health inspector, are you going to display it or not? You’re going to display it, right? Because why not? we know the A’s are going to display, right, these certificates are being given to everybody, so you’re going to display even a B certificate. Now I’m told from people who lived in Los Angeles at the time that you could go around to the greasiest spoon in Los Angeles and look through these grease-smeared windows with the cockroaches running all up and down them, and if you look carefully behind the cockroaches and the grease, you’d see a certificate displayed that said C on it, right? Presumably there was a D grade as well. Even the C’s were displaying, all right? So that’s pretty dramatic information unraveling. Now I’m exaggerating slightly to make a separate point. It turns out that in certain areas of Los Angeles, you’d expect to see these health certificates displayed, even the C’s, right? And in other areas, you wouldn’t expect to see the C’s displayed. Which areas would you expect not to see people bothering displaying their C or B- certificates? Any guesses? The tourist areas, right? The tourist areas. Because for this story about information unraveling to work, theFor this story about information unraveling to work, the people who are the receivers of the information need to know that you got the certificates.

[译文 16]

所以你仍然从洛杉矶健康检查员那里得到B证书，你会展示它还是不展示？你会展示它，对吧？因为为什么不呢？我们知道A会展示，对吧，这些证书是发给每个人的，所以即使是一个B证书你也会展示。现在我被住在洛杉矶的人告诉我，你可以去洛杉矶最油腻的餐馆，透过那些沾满油脂的窗户看，蟑螂在上下乱爬，如果你仔细看，在蟑螂和油脂后面，你会看到一张证书展示着C，对吧？大概也有D等级。即使是C也在展示，好吗？所以这是相当戏剧性的信息泄露。现在我稍微夸张了一点来说明一个不同的问题。事实证明，在洛杉矶的某些地区，你会期望看到这些健康证书被展示，甚至是C，对吧？而在其他地区，你不会期望看到C被展示。你会期望在哪些地区看不到人们费心展示他们的C或B-证书？任何猜测吗？旅游区，对吧？旅游区。因为对于这个关于信息泄露的故事起作用，信息的接收者需要知道你们获得了证书。所以如果你是洛杉矶的游客，你知道这个系统已经到位，因此如果你是C证书，就在迪士尼乐园旁边或其他什么地方，你仍然可以在不告诉他们你即将这样做的情况下做成一些旅游生意。所以这是第二个例子。让我举第三个例子，稍微接近家一点的。在上一次课程改革时，耶鲁大学关于学分不及格的问题进行了一场大辩论。其中一个关于学分不及格的提议是允许学生以学分不及格的方式修课，但如果他们最终获得了A或B，他们可以在简历上展示A或B。所以他们以学分不及格的方式修课，但如果他们得到了一个分数，比如A或B，A-，不管什么，然后他们可以选择加入并把它放在简历上。这个提议有什么问题？这是一个严肃的提议。我在委员会上，对吧？这个提议是认真提出的。我没有提出这个提议，但这是认真提出的，对吧？这个提议有什么问题？这个提议有什么问题？在成绩单上展示学分不及格意味着什么？它意味着C，对吧？它意味着C。因为所有的A和B都会泄露信息。所以如果信息是可验证的并且可以自由传递，它有办法暴露出来。

[段 17]

So if you’re a tourist in Los Angeles, you know the system’s in place, and therefore if you’re a C certificate right next to Disneyland or something, whatever it is, you can still make some tourist sale without having to tell them you’re about to do so. So that’s a second example. Let me give a third example a little bit closer to home. At the last curriculum reform at Yale, there was a big debate about what to do with credit defail. And one of the proposals for credit defail was to allow students to take courses credit defail, but if they ended up getting an A or a B, they could display the A or the B on their resume. So they take it credit defail, but if they got a grade, like an A or a B, an A-, whatever, then they could opt in and have it put on their resume. What’s wrong with that? This is a serious proposal. I was on this committee, right? This was seriously made. I didn’t make the proposal, but this was made, right? What’s wrong with this proposal? What’s wrong with the proposal? What would displaying credit on your transcript come to mean? It would come to mean C, right? It would come to mean C. Because all the A’s and the B’s would unravel the information. So if information is verifiable and can be freely transmitted, it has a way of coming out.

[译文 17]

它有办法暴露出来。它有办法暴露出来。让我举一个稍微更严肃的例子。你们都知道，如果你在美国被捕，你应该知道这一点，你有权保持沉默。我不是说你们都要被捕，但如果你被捕，你有权保持沉默。这个权利在英国也是如此，直到最近，政府不太重视公民自由，稍微改变了规则。所以现在你在英国有权保持沉默，但法院有权将你保持沉默作为证据加以考虑。好吧？那这对保持沉默的权利做了什么？我留给你们去弄清楚这对保持沉默的权利做了什么。好吧。所以这是一个领域。这个关于信息泄露的想法取决于某些关键部分。其中最重要的部分是信息是可验证的。信息是可验证的很重要的是，要获得完全的泄露，一直到底，在这个案例中是成本最高的机构，你需要信息接收端的人实际上知道那些信息就在那里。所以要获得完全的泄露，你真的需要类似关于信息存在的共同知识。

[段 18]

It has a way of coming.has a way of coming out. It has a way of coming out. Let me give you one slightly more serious example. As you all know, if you’re arrested in the US, you should know this, you have the right to remain silent. I’m not saying you’re all about to get arrested, but were you to be arrested, you have the right to remain silent. That right was true in Britain as well until recently, when the government, which isn’t so big on civil liberties, changed the rule slightly. So now you have the right to remain silent in Britain, but the court has the right to take into account as evidence if you remain silent. All right? So what’s that done to the right to remain silent? I’ll leave it to you to figure out what that’s done to the right to remain silent. All right. So this is an area. This idea that information unravels depended on certain key parts. And the most important part was that the information was verifiable. It mattered that the information was verifiable, and to get full unraveling, all the way down, in this case, to the highest cost firm, you needed the people on the receiving side of the information to actually know that that information was there. So to get the full unraveling, you really need something like common knowledge of the presence of the information.

[译文 18]

这个关于信息泄露的想法取决于某些关键部分。其中最重要的部分是信息是可验证的。信息是可验证的很重要的是，要获得完全的泄露，一直到底，在这个案例中是成本最高的机构，你需要信息接收端的人实际上知道那些信息就在那里。所以要获得完全的泄露，你真的需要类似关于信息存在的共同知识。

[段 19]

All right? But often, the information that you have, you have information, you want to reveal that information, but unfortunately it’s not so easily verifiable. So what we’re going to focus on for the rest of the day is information verification.on for the rest of the day is information that is not verifiable. All right and let’s start with an example that’s pretty close to home. A lot of you have been doing job interviews recently. How many of you’ve been going out either doing interviews for internships or jobs and I know a lot of you are missing class, I’m assuming charitably that’s what you were doing. All right? All right? So when you go to these job interviews, you can imagine that you’re turning up for some job interview. Let’s say it’s at Boring Bank of Boston. All right? And you turn up at this interview for Boring Bank of Boston. And one of the things that Boring Bank of Boston wants to know is, are you interested in working for Boring Bank of Boston? All right? That’s a plus for them. All right? So what they tend to do is they ask you, more or less, they say, are you interested in working for Boring Bank? Now, by the way, if you are asked the question, and you’re interviewing for Boring Bank, and you’re asked the question by them, are you interested in working for Boring Bank, what answer should you give?

[译文 19]

好的？但通常情况下，你拥有的信息，你想要透露这些信息，但遗憾的是这些信息并不是那么容易验证的。那么我们今天剩余时间要关注的是无法验证的信息。好吧，让我们从一个贴近生活的例子开始。你们中很多人最近都在参加工作面试。有多少人出去参加实习或工作面试，我知道你们中很多人翘课了，我善意地假设你们翘课就是为了这个。好吧？好吧？那么当你们参加这些工作面试时，你可以想象自己来参加某个工作面试。假设是在波士顿无聊银行。好吧？你来到波士顿无聊银行参加面试。波士顿无聊银行想知道的事情之一是，你是否有兴趣为波士顿无聊银行工作？好吧？对他们来说这是个加分项。好吧？那么他们通常会问你什么呢？他们或多或少会问，你有兴趣为无聊银行工作吗？现在，顺便说一下，如果你被问到这个问题，而且你正在为无聊银行面试，他们问你是否有兴趣为无聊银行工作，你应该怎么回答？

[段 20]

You should answer yes. How much information is there in the fact you answer yes? None at all, right? because clearly you want the option of working for this bank, so you’re going to answer yes anyway. Now you may think this is just a fictional example. It’s not.may think this is just a fictional example. It’s not. I talked to some recruiters from a bank in Boston that we’ll refer to as Boring Bank in Boston not so long ago, and I asked them about hiring Yale undergraduates and what Yale undergraduates do to impress them. And the recruiter, who was a Yale graduate himself, said to me that, frankly, Yale undergraduates do less well in these interviews than Harvard undergraduates. And I said, you know, chattered and disappointed. I said, why? And he said, well, when we asked them if they’re interested in working for Boring Bank of Boston, the Yale guys say things like, well, I don’t know, it sounds kind of boring. And the Harvard guys, what do they do? They show up with the Wall Street Journal folded over conveniently on the page about Boring Bank of Boston, and sometimes they’re wearing a silly hat with I’m boring on it. So I tried to persuade this guy that despite this fact, there’s really no information in the fact that the Harvard guys are telling this, and in fact you should hire the Yale people because at least they were honest and hey that might make the bank less boring in the future.

[译文 20]

你应该回答是的。你回答"是的"这个事实包含多少信息？完全没有，对吧？因为很明显你想要为这家银行工作的选择，所以你无论如何都会回答是的。你可能认为这只是一个虚构的例子。但实际上并非如此。我不久前与波士顿一家银行的招聘人员交谈过，我们称之为波士顿无聊银行，我问他们关于招聘耶鲁本科生的问题，以及耶鲁本科生如何给他们留下深刻印象。这位招聘人员自己也是耶鲁毕业生，他对我说，坦率地说，耶鲁本科生在这些面试中的表现不如哈佛本科生。我说，你知道的，我感到惊讶并失望。我说，为什么？他说，呃，当我们问他们是否有兴趣为波士顿无聊银行工作时，耶鲁的家伙们会说诸如"嗯，我不知道，听起来有点无聊"之类的话。哈佛的家伙们会怎么做呢？他们会带着《华尔街日报》，巧妙地翻到关于波士顿无聊银行的页面，有时候还戴着写有"我很无聊"的傻帽子。所以我试图说服这个人，尽管有这个事实，哈佛家伙们所说的话实际上并没有任何信息，实际上你应该雇用耶鲁的人，因为至少他们是诚实的，而且嘿，这可能会让银行未来不那么无聊。

[段 21]

This didn’t work. So I need to persuade you guys to actually cough up and be dishonest here. There’s a lesson here, so one lesson is if you are asked by an interviewer at one of these, for a summer internship or for a job later if you want to work for them the answer is yes all right it’s one of the few questions which the answer is not backward inductionAll right, it’s one of the few questions which the answer is not backward induction, it’s just yes. There’s a secondary lesson here, which is if an interviewer for a bank is asking you in the interview if you’d like to work for them, you probably, you answer yes, but you probably want to work somewhere else. If they’re dumb enough to ask you that question, you probably want to work for someone else. All right, but this is a real problem. The problem is, here you are, you have some information you’d like to convey. Maybe you really are boring. Maybe you really do want to work for this bank. You want to convey this information, but it’s hard for you to persuade the employer that this is true, because anybody can say they want to work for the bank. And more generally in life, it isn’t only about whether you want to work for a particular bank or whatever it happens to be.

[译文 21]

这没有奏效。所以我需要说服你们在这里真正地配合并且不诚实。这里有一个教训，所以一个教训是，如果你被这些地方的面试官问到暑期实习或者以后的工作，如果你想为他们工作，答案就是是的，好吧，这是少数几个答案不是逆向归纳的问题之一，好吧，这是少数几个答案不是逆向归纳的问题之一，答案就是是的。这里还有第二个教训，如果银行的面试官在面试中问你是否愿意为他们工作，你可能，你应该回答是的，但你可能实际上想去别的地方工作。如果他们笨到问你这个问题，你可能想去为别人工作。好吧，但这是一个真正的问题。问题是，你在这里，你有一些信息想要传达。也许你真的很无聊。也许你真的想为这家银行工作。你想传达这些信息，但你很难让雇主相信这是真的，因为任何人都可以说他们想为银行工作。更一般地说，在生活中，这不仅仅是关于你是否想为某家特定的银行或任何碰巧的情况有关。

[段 22]

It’s also about whether you are a good worker or not. so let’s try and think about this in the context of not workers being boring or not but workers being good or not so we’re going to look at a costly signaling model it’s going to turn out this model is going to be about costly signaling and just for the purpose of the model we’re going to assume that there are two kinds of workers in America there are good workers we’ll call them G and there are bad workers. And we’ll call thembad workers and we’ll call them B. Alright? And we’ll assume that the productivity of a good worker, if you work for this firm, is going to be 50. And we can assume this is $50,000 or whatever, but let’s forget units for now and just call it 50. And a bad worker, their productivity is only 30. Alright? So clearly, all other things being equal, the employer would rather employ a good worker or a bad worker. All other things being equal is important because then we have to pay the good worker more. Let’s assume this is the U.S. economy. So roughly 10% of the economy are good workers and 90% are bad workers. Something like that. These are the proportions in the U.S. And let’s also assume that firms are competitive. So firms are flooding into the Yale Careers Office or the Yale Careers Fair and they’re just desperately trying to hire these workers.

[译文 22]

这也关于你是否是一个好员工。所以让我们在员工是否无聊的背景下思考这个问题，但不仅仅是员工是否无聊，而是员工是好还是不好，所以我们将看一个代价信号模型，事实证明这个模型将是关于代价信号的，仅仅为了模型的目的，我们将假设在美国有两种员工，有好员工，我们称之为G，有坏员工。好吧？我们将称之为坏员工，我们将称之为B。好吧？我们将假设一个好员工的 productivity，如果你在该公司工作，将是50。我们可以假设这是50,000美元或什么的，但现在让我们忽略单位，就称之为50。而一个坏员工的 productivity 只有30。好吧？很明显，在其他条件相同的情况下，雇主宁愿雇用一个好员工而不是坏员工。其他条件相同是很重要的，因为我们必须为好员工支付更多。让我们假设这是美国经济。所以大约10%的经济是好员工，90%是坏员工。大致是这样的。这些是美国经济中的比例。我们也假设公司是竞争性的。所以公司涌入耶鲁职业办公室或耶鲁招聘会，他们拼命地想要雇用这些员工。

[段 23]

There’s competitive hiring going on. All right? So firms compete for workers. So they’re going to pay 50 to a worker they identify as good. to a worker they, the firms, identify as good and theyas good, and they’re going to pay 30 to workers they identify as bad. If you’re bothered by this being exact, think of it as 50 minus a penny and 30 minus a penny. It’s not going to make any difference to the analysis. So if they can’t identify a worker, they think the worker is just the average worker, how much will the competitive wage be? What would the competitive wage of the average worker in this economy? It’s not a hard math question. Everyone’s scratching their head down here. All right, so this is, what is it? It’s 50 times 10% and 30 times 90%, which averages out as? 32%, all right? So they’ll pay the average, which is 32, to a worker they cannot identify. All right. Now clearly in this model, much like in the high-cost firms we started with, the good workers would like to be identified. Is that right? Because they get paid more. And the bad workers do not want to be identified. Is that right? They’d rather remain hidden. The problem here, however, is there typically isn’t a verifiable piece of information.

[译文 23]

有竞争性的招聘在进行。好吧？公司争夺员工。所以他们将支付50给一个他们认定为好的员工。他们将支付30给被认定为坏的员工。如果你对这个精确性感到困扰，想象成50减一便士和30减一便士。这不会对分析产生任何影响。那么如果他们无法识别一个员工，他们认为这个员工就是普通员工，竞争性工资会是多少？在这个经济体中普通员工的竞争性工资是多少？这不是一个困难的数学问题。每个人都在这里挠头。好吧，所以这是，什么？它是50乘以10%加上30乘以90%，平均值是？32%，好吧？所以他们将支付平均值，即32，给一个他们无法识别的员工。好吧。现在很明显，在这个模型中，就像我们最初开始的高成本公司一样，好员工希望被识别。对吧？因为他们会得到更多报酬。而坏员工不希望被识别。对吧？他们宁愿保持隐藏。然而，这里的问题是，通常没有可验证的信息。

[段 24]

It’s hard to verifiably communicate to the other side that you’re a good worker.to the other side that you’re a good worker so you guys are all good workers right you wouldn’t be here otherwise we hope all right so you you show up to this firm this firm is looking for good workers and you could tell the firm I’m a good worker in fact I’m getting betting most of you have tried doing that in your job interviews right I’m a good worker you could even do this in a costly manner right you could you could humiliate yourself by jumping up on the table and dancing on one leg while singing some song about how you’re a good worker. All right? Which would be humiliating, but it wouldn’t, in fact, communicate to the firm that you were a good worker. Why is it that you’re dancing this beautiful jig on the table of the interview room, singing this beautiful song about how you’re a good worker? Why doesn’t that convince the firm that you’re a good worker? Who’s been in job interviews recently? Has anyone tried this? Why is that not a successful strategy? Yes, so Stephen, is that right? Shout out? A bad worker could do that too. A bad worker could do that too. So it’s true that it’s costly and humiliating to dance up on the table on one leg and sing you’re a good worker, but it’s no more costly and humiliating for you than it is for a bad worker.

[译文 24]

很难向对方可验证地传达你是一个好员工。所以你们都是好员工，对吧？否则你不会在这里，我们希望如此，好吧，所以你你来到这家公司，这家公司正在寻找好员工，你可以告诉公司我是一个好员工，事实上我打赌你们大多数人在工作面试中都试过这样做，对吧？我是一个好员工。你甚至可以以一种代价高昂的方式这样做，对吧？你可以你可以通过跳到桌子上单脚跳舞，同时唱一首关于你是一个好员工的歌来羞辱自己。好吧？那会是羞辱人的，但实际上它不会向公司传达你是一个好工人。为什么你在面试室的桌子上跳着美丽的 jig，唱着关于你是一个好员工的美丽歌曲？为什么这不能让公司相信你是一个好员工？最近谁参加过工作面试？有人试过这个吗？为什么这不是一个成功的策略？是的，所以斯蒂芬，对吧？大声说出来？一个坏员工也可以那样做。一个坏员工也可以那样做。所以这是真的，在桌子上单脚跳舞并唱你是好员工是代价高昂和羞辱人的，但对于你来说，它并不比为坏员工代价更高和更羞辱人。

[段 25]

So if that worked, a bad worker would do it too. So merely a song and dance isn’t going to work. Merely a song and dance isn’t going to work. It’s going to be hard to signal to the outside.it’s going to be hard to signal to the outside world that you’re a good worker. All right? And that’s going to be our starting point. All right? So we need a way for good workers to distinguish themselves from bad workers. We need a way for them to signal. and what’s key about that signal is it has to be a signal that they can make and a bad worker cannot make. Or, alternatively, a signal that they will want to make but a bad worker will not want to make. So dancing on the table doesn’t do it and the reason it doesn’t do it is bad workers and good workers are symmetric with respect to the dishonor of dancing on the table. alright so we need a way for good workers you guys to distinguish yourself from bad workers, us guys alright how in the American economy what’s the mean way in the American economy in which good workers signal the fact that they’re good that they manage to distinguish themselves what’s the mean signal used in the US economy somebody education alright so the main signal the main signal in the US not the only one by any means but the main signal isis education.

[译文 25]

所以如果这能起作用，一个糟糕的工人也能做到。因此仅仅唱歌跳舞是不行的。仅仅唱歌跳舞是不行的。这将很难向外部世界发出信号。这将很难向外部世界发出信号，表明你是一个好员工。明白吗？这就是我们的出发点。明白吗？所以我们需要一种方法让好员工与坏员工区分开来。我们需要一种方法让他们发出信号。而这个信号的关键在于，它必须是一个好员工能够发出而坏员工无法发出的信号。或者换一个角度，是一个好员工愿意发出而坏员工不愿意发出的信号。所以在桌上跳舞做不到，原因在于坏员工和好员工在跳舞的丢脸程度上是对称的。好的，所以我们需要一种方法让好员工你们把自己与坏员工我们区分开来。在美国经济中，好员工是如何发出信号表明自己是好员工的？他们是如何做到区分自己的？在美国经济中使用的主要信号是什么？有人说是教育。好的，所以主要信号，美国的主要信号，绝不是唯一一个，但主要信号是教育。

[段 26]

What’s going to distinguish the good workers from the bad workers is the good workers are going to have degrees, more degrees, better degrees, more degrees, whatever. So what we’re going to look at today is a model some of you have seen before, but we’ll do it in a bit more detail perhaps. It’s a model due to a guy called Spence, Mike Spence, who actually won the Nobel Prize in large part for this model. The reason we know he won the Nobel Prize in large part for this model is he didn’t write practically anything else. So it must have been for this model. All right. So what we’re going to do is we’re going to imagine that the degree, the education that these people are going to get that’s going to distinguish themselves and show that they’re good workers to the employers, it’s assumed that the employees, once again, are banks or whatever, we’re going to assume that the extra piece of education they’re going to get is an MBA. Some of you up there are getting an MBA. Where’s my MBA student up there? So the good workers are going to get an MBA. And the way this is going to work it’s going to work on the cost of getting an MBA. So to get this to be a successful signal to make this signal different from merely dancing on the table it’s either going to be the case that bad workers cannot get an MBA, or it’s got to be the case that it’s so costly for bad workers to get an MBA that they won’t bother.

[译文 26]

能够区分好员工和坏员工的是，好员工会有学位，更多的学位，更好的学位，各种学位。所以今天我们要看的是一个模型，你们中有些人以前见过，但我们可能会更详细地讲一下。这是一个由一位叫斯宾塞的人建立的模型，迈克·斯宾塞，他实际上获得了诺贝尔奖，很大程度上就是因为这个模型。我们知道他很大程度上是因为这个模型获奖的原因是，他实际上没写过什么其他东西。所以肯定是因为这个模型。好的，那么我们要做的是，我们想象这些人要获得的学位和教育，这将让他们区分自己，并向雇主展示他们是好的员工，我们假设员工，再次说明，是银行或其他什么机构，我们假设他们要获得的额外教育是MBA。你们中有些人正在读MBA。我的MBA学生在哪里？好的，好员工会获得MBA。而这将如何起作用，它将通过对获得MBA的成本起作用。所以要使这成为一个成功的信号，使这个信号不同于仅仅在桌上跳舞，要么是坏员工无法获得MBA，要么是对于坏员工来说获得MBA代价太高以至于他们不会去费心。

[段 27]

All right? So we’re going to make the difference in costs. All right? So we’re going to suppose that the cost per year of getting an MBA, of being in business school, so of MBA education of MBA education is five five units if you’re a good worker and we’re going to assume that the cost per year of going to SOM and getting an MBA is a little bit over ten so ten and a penny if you’re a bad worker. So notice, I’ve assumed in this model that it’s more costly per year to get an MBA at Yale, say, if you’re a bad worker than a good worker. Now what are those costs? What are the costs of getting an MBA? What’s causing that cost difference? Well, let’s be clear what it isn’t. It can’t be the fees. The fees are a large part of the cost.

[译文 27]

明白吗？所以我们要制造成本的差异。明白吗？所以我们要假设获得MBA的成本，每年的成本，在商学院学习的成本，MBA教育的成本，如果你是一个好员工是5个单位，而我们要假设如果你是一个坏员工，在SOM读MBA并获得学位的成本略高于10，所以是十块零一分钱。注意，我在这个模型中假设，如果你是一个坏员工，在耶鲁读MBA每年比一个好员工更贵。这些成本是什么？获得MBA的成本是什么？是什么导致了这种成本差异？好的，让我们明确它不是什么。它不可能是学费。学费是成本的一个大部分。

[段 28]

What are the fees of getting an MBA at Yale?fees are a large part of the cost of the field one of the fees are getting an MBA at Yale this year way too much all right right so the cost per year in terms of fees are enormous but the fees themselves are not going to do a good job of distinguishing between good and bad workers why because they’re the same for both parties right we want that we want something which is differently costly so this is not this is not the fees it can’t be the fees they’re the same for both parties what other costs are there what other costs are there to getting an education there’s opportunity cost right all of you are economists or half of you are economics majors so the first thing you should spring to mind is opportunity costs all right but actually opportunity costs don’t help me here much because if anything you’d think that the opportunity costs of going and getting an MBA at Yale are higher if you’re a good worker than if you’re a bad worker after all if you’re a good worker you could stay home not get an MBA farm your farm your parents garden all right and you’re such a good worker you’d have a high yield in carrots and whatever all right all right all right so it where’s the bad workers and not going to produce anything right so this is not really about opportunity cost in fact we’ll assume that there’s zero we’ll assume there are no opportunity costs so what is it that’s driving this cost difference between the good worker at SOM and the bad worker at SOM.

[译文 28]

获得MBA的学费是多少？学费是获得MBA成本的一个很大部分。在耶鲁获得MBA的学费是巨大的，但学费本身无法很好地区分好员工和坏员工。为什么？因为对双方来说学费是一样的，对吧。我们想要的是成本不同的东西，所以这不是学费，不可能是学费，它们对双方是一样的。还有什么其他成本？获得教育还有什么其他成本？有机会成本，对吧。你们都是经济学家，或者你们一半是经济学专业，所以你们首先应该想到的就是机会成本。好的，但实际上机会成本对我帮助不大，因为如果说有什么的话，你会认为在耶鲁读MBA的机会成本，如果你是一个好员工，比如果你是一个坏员工更高。毕竟，如果你是一个好员工，你可以待在家里，不读MBA，耕种你父母的园子，对吧，而你是一个这么好的员工，你种植胡萝卜的产量会很高，什么都行。好的，好的，所以坏员工不会生产任何东西，对吧。所以这实际上与机会成本无关，实际上我们会假设没有机会成本，假设机会成本为零。那么，是什么在推动好员工在SOM和坏员工在SOM之间的成本差异呢？

[段 29]

Was that a potential answer out there? Yeah.Was that a potential answer out there? Yeah. Is it the present value of future wages for a good worker? Ah, okay. So there we’re thinking about the future. No, let’s just focus on the cost side. Let’s focus on the cost side. You’re right, there’s going to be different things going on in the future, but let’s focus on the cost side. I had you before, so let’s have this guy. Mental effort? Mental effort, right? Mental effort. So where’s my MBA student up there? Here he is. Where is he? Up there. all right it’s pain and suffering right right and I can’t see him yet there is it’s pain and suffering that right he’s nodding good right right it’s having it’s having that when you go to the MBA class of thinking my god I thank goodness I escaped being undergraduates and you go back to the MBA class and I’m there again right I’m saying the same horrible problem sets and you still can’t read my handwriting and you still deal with my accents right good workers find it easier to read my handwriting and deal with my accent right all right all right So what it is, it’s the mental effort. It’s the pain and suffering. It’s the pain of the work. It’s the pain of the work.

[译文 29]

那边有人回答了吗？是的。那边有人回答了吗？是的。是好员工未来工资的现值吗？啊，好的。所以我们在考虑未来。不，让我们只关注成本方面。让我们关注成本方面。你说得对，未来的事情会有各种不同的情况，但让我们关注成本方面。我之前问过你，所以让这个人来回答。脑力劳动？脑力劳动，对。脑力劳动。所以我的MBA学生在哪里？在这里。他在哪里？上面。好的，这很痛苦，这是痛苦，对吧，我还没看到他，是的，这是痛苦，对吧，这就是当你走进MBA课堂时的感觉，哦我的天哪，谢天谢地我逃过了本科生的日子，然后你回到MBA课堂，我又来了，我又在做同样的可怕的习题集，你们还是看不懂我的笔迹，还是在应付我的口音。好的，好员工更容易看懂我的笔迹并应付我的口音。好的，好的。所以这，就是脑力劳动。是痛苦和折磨。是工作的痛苦。是工作的痛苦。

[段 30]

The only thing that distinguishes the costs of good workers from bad workers in education is it’s so painful to do the work. If we went to a party school, this wouldn’t work. We can’t just have party schools. We actually have to put you through some pain in the classroom. I’m looking for some confirmation from up there. All right?Some confirmation from up there. All right? So the pain of the work is what distinguishes these things. Okay. Now, I claim that we can have an equilibrium in this society in which there are good and bad workers, in which good workers’ cost per year is less than bad workers’ cost per year of getting, in this case, an MBA. We do the same for undergraduate education. Let’s focus on the MBA for now. I claim there’s an equilibrium in the society, there could be an equilibrium, in which getting an MBA takes three years. So I claim there is an equilibrium here, an equilibrium in which what happens? in which there are three-year degrees. Degrees take three years. Three-year MBA sounds a bit frightening, but never mind. In which the good workers all get MBAs, and the bad workers do not. all right but to tell you this is an equilibrium into a little bit more so let me tell you one other thingto tell you this is an equilibrium, we need to do a little bit more.

[译文 30]

在教育中唯一能区分好员工和坏员工成本的东西，就是做这项工作太痛苦了。如果我们去了一个派对学校，这就不行了。我们不能只有派对学校。我们实际上需要在课堂上让你们经历一些痛苦。我在寻找那边的确认。好的？那边的确认。好的？所以工作的痛苦是区分这些东西的东西。好的。现在，我声称我们可以在这个社会中有一个均衡，其中有好员工和坏员工，其中好员工每年的成本低于坏员工每年的成本，获得MBA，在这个例子中是MBA的成本。我们对本科教育也做同样的事。让我们先只关注MBA。我声称这个社会可能存在一个均衡，在其中获得MBA需要三年。所以我声称这里存在一个均衡，一个什么样的均衡？在其中有三年制的学位。学位需要三年。三年制MBA听起来有点吓人，但没关系。其中好员工都获得MBA，而坏员工不获得。好的，但要告诉你这是一个均衡，我们需要再做一些说明。

[段 31]

So let me tell you one other thing. So I claim there’s an equilibrium in which the degrees take three years, all the good workers get MBAs, all the bad workers do not get MBAs, and what? And the employers identify MBAs as good workers. To make this work, it has to convince the employers. So to make it work, I need and the employers identify MBA equals good and not MBA equals bad. All right. So that’s what I claim as an equilibrium here. And what I want to do is, I want us to show that this actually is an equilibrium. All right. Now then, this is a slightly different kind of equilibrium to anything we’ve seen in the class so far. So I’m going to be a little bit slow and nerdy about what we need to check to check that this indeed is an equilibrium. All right, so I’m going to leave some space on the board, and you should leave some space, too. All right, so my claim is this is an equilibrium, and we’re doing guess and check. I did the guess for you, and we’ll do the check together.I did the guess for you. We’ll do the check together. To check, I claim I need to check two things. Two things.

[译文 31]

那么让我告诉你另一件事。我声称存在一个均衡，在其中学位需要三年时间，所有优秀员工都获得MBA，所有差劲员工不获得MBA，然后呢？雇主会把MBA识别为优秀员工。为了使这个均衡成立，它必须说服雇主。所以为了使其成立，我需要雇主将MBA等同于优秀，而非MBA等同于差劲。好的。这就是我在这里声称的均衡。那么我想做的是，我想让大家证明这确实是一个均衡。好的。现在，这是一种与我们迄今为止在课堂上看到的任何均衡都略有不同的均衡。所以我会稍微慢一点、啰嗦一点地说明我们需要检查什么，以确认这确实是一个均衡。好的，我在黑板上留一些空间，你们也应该留一些空间。好的，我的断言是这是一个均衡，我们正在进行猜测和验证。我已经为你们做了猜测，我们将一起做验证。我为你们做了猜测。我们将一起做验证。为了验证，我声称我需要检查两件事。两件事。

[段 32]

Alright, one, I need to check that no type will deviate. so what I mean by a type I mean types of worker neither the good types of workers will want to deviate nor the bad types of worker will want to deviate so this isn’t new we’ve all when we’ve checked equilibrium we’ve always checked that people don’t want to deviate the only slight difference here is instead of checking that people won’t want to deviate I’m checking that types of people won’t want to deviate but basically the idea is the same is that right now it is the same, so this is not really new the new thing is I also need to check actually I’ll give myself a bit more room here I also need to check I need to check that the employer’s beliefs the employer’s beliefs are consistent consistentconsisted with the equilibrium behavior. All right? So let’s just stop and pause at that a second. We’ve never written down a condition like this for equilibrium, but here I have to. Here, there was asymmetric information in the model, and in this equilibrium, one important party to the equilibrium, namely the guys who are going to employ you, that’s pretty important, right? All they really have to do in this model of any importance is form an inference based on your actions. They observe whether you get an education or not and they conclude whether or not you’re a good or bad worker.

[译文 32]

好的，第一，我需要检查没有任何类型会偏离。所以我所说的类型，我指的是工人类型，无论是优秀类型的工人还是差劲类型的工人，都不会想要偏离。所以这并不新鲜，我们所有人，当我们在检查均衡时，总是检查人们不想偏离。这里唯一的轻微区别是，我检查的不是人们不会想要偏离，而是类型的 人们不会想要偏离，但基本上想法是相同的，就是现在它是一样的，所以这真的不是什么新鲜事。新鲜的事情是，我还需要检查，实际上让我在这里给自己多一点空间，我还需要检查我需要检查雇主的信念雇主的信念与均衡行为一致一致。好的？让我们就此停下来暂停一下。我们从来没有为均衡写过这样的条件，但在这里我必须这样做。在这个模型中存在非对称信息，而在这个均衡中，均衡的一方非常重要，那就是将要雇佣你的人，那非常重要，对吧？在这个模型中，他们真正需要做的最重要的事情就是根据你的行为进行推断。他们观察你是否获得了教育，并推断你是优秀工人还是差劲工人。

[段 33]

So we’re going to write down as a condition of this being an equilibrium that those inferences, quote, make sense, unquote. And by make sense, I mean that they’re consistent with what actually is happening in equilibrium. So before we get too nerdy about that, let’s just think why that’s a sensible thing to require. Suppose, in fact, suppose the world was like this. All good workers got MBAs. All bad workers did not get MBAs. And employers thought that the people who got MBAs were half good and half bad. All right? That doesn’t sound right, right? If in fact it’s the case that it’s the good workers who are getting MBAs and the bad workers who are not,workers are getting MBAs and the bad workers who are not, then the only belief that the employers can have that’s consistent is the MBAs are in fact the good workers and the non-MBAs are the bad workers. Is that right? So I’m not making any deep point here, I’m just pointing out that we need to make sure that the beliefs that people hold in this equilibrium are consistent with what’s actually going on in the equilibrium. Now having said that, there’s no mystery here, everything’s fine. In this particular claim of an equilibrium, good workers are the ones who got the MBAs, bad workers are the ones who didn’t get the MBAs, and the employers when they see an MBA indeed think they’re good, and when they see a non-MBA they indeed think they’re bad.

[译文 33]

所以我们将把这个作为一个条件写下来，即这确实是一个均衡，那些推断，引号，正确合理 unquote。而所谓 make sense，我的意思是它们与均衡中实际发生的事情一致。在我们对此过于唠叨之前，让我们想想为什么要求这一点是合理的。假设，事实上，假设世界是这样的。所有优秀工人都获得了MBA。所有差劲工人都没有获得MBA。而雇主认为获得MBA的人一半是优秀的，一半是差劲的。好的？那听起来不对，对吧？如果事实上是优秀工人获得MBA，差劲工人没有获得MBA，那么雇主唯一能持有的与之一致的信念就是 MBA 实际上是优秀工人，而非 MBA 是差劲工人。对吧？我在这里没有提出什么深刻的观点，我只是指出我们需要确保人们在这个均衡中持有的信念与均衡中实际发生的事情一致。现在，话虽如此，这里没有神秘之处，一切都很好。在这个特定的均衡声明中，获得 MBA 的是优秀工人，没有获得 MBA 的是差劲工人，而雇主当他们看到 MBA 时确实认为他们是优秀的，而当他们看到非 MBA 时他们确实认为他们是差劲的。

[段 34]

So these beliefs are in fact consistent with behavior. So we’re okay. Okay so I’ve had to check that but it wasn’t a big deal. Everyone okay about why I’m checking it? I don’t want people to whole silly beliefs in equilibrium. That’s basically what I’m saying. All right. Now let’s go back and check the sort of bread and butter thing. The bread and butter thing is we need to check that no type of worker is going to want to deviate in this equilibrium. So there’s two types of worker. There’s good workers. And good workers, what are they doing in equilibrium? What are the good workers doing an equilibrium? They’re getting an MBA. So the good workers, they become MBAs. And what are the good workers identified as?And what are the good workers identified as? Once they’ve got an MBA, what does the employer identify them as? Good workers, right? They’re identified as good. They get MBAs. They’re identified as good. And their payoff is what? What’s the payoff of the good workers here? so they get paid they get paid 50 which is their productivity but it cost them 3 years of putting up with my homeworks so it cost them 3 times 5 5 for each year so 50 minus 3 times 5 is what?

[译文 34]

所以这些信念实际上与行为一致。所以我们没问题。好的，所以我不得不检查这一点，但这不是什么大事。每个人都知道我为什么检查它吗？我不希望人们在均衡中有愚蠢的信念。这基本上就是我所说的。好的。现在让我们回去检查那种基础性的东西。基础性的东西是我们需要检查在这个均衡中，没有任何类型的工人会想要偏离。所以有两种类型的工人。有优秀工人。那么优秀工人在均衡中做什么？优秀工人在均衡中做什么？他们获得 MBA。所以优秀工人，他们成为 MBA。而优秀工人被识别为什么？优秀工人被识别为什么？一旦他们获得了 MBA，雇主识别他们是什么？优秀工人，对吧？他们被识别为优秀。他们获得 MBA。他们被识别为优秀。他们的收益是什么？这里优秀工人的收益是多少？他们获得报酬他们获得报酬 50，这是他们的生产力，但代价是他们忍受我的作业三年，所以代价是 3 乘以 5，每年的费用是 5，所以 50 减去 3 乘以 5 是多少？

[段 35]

50 minus 3 times 5 is 35 so they get a total payoff of 35 and let me just pause a second, I made an assumption here without telling you it so I’m going to say it, just to make the math simple we’ll assume that once you get employed you work for a year and then you drop dead that’s a slightly morbid and unpleasant assumption but otherwise we have to do present discounted value of your whole future income and it turns into an accounting class so we’ll just assume everybody lives for one year if you want to do a more complicated model then that’s fine, the idea will be the same So they get paid 50, it’s cost them 3 times 5, and they get a total payoff of 35. How about if they deviate?All right? How about if they deviate? If they deviate, that means they don’t get MBAs, so they’re not MBAs. They’re identified what? If they don’t get an MBA, what are they identified as? What does the employer think the non-MBAs are? Bad, all right? So if they deviate, then the employers think they’re bad, even if they dance on the table and say they’re good. They’re in fact bad. They’re identified as bad. And so their payoff is what? What are they going to get paid? They’re going to get paid 30.

[译文 35]

50 减去 3 乘以 5 是 35，所以他们获得的总收益是 35，让我暂停一下，我在这里做了一个假设而没有告诉你们，所以我现在要说出来，为了让数学简单，我们假设一旦你被雇用，你工作一年然后就死了，这是一个稍微病态和不愉快的假设，但否则我们必须对你整个未来收入进行现值计算，那就变成了一堂会计课，所以我们假设每个人都活一年如果你想做一个更复杂的模型那也可以，想法是一样的所以他们获得 50 的报酬，代价是 3 乘以 5，他们获得的总收益是 35。如果他们偏离呢？好的？如果他们偏离呢？如果他们偏离，这意味着他们不获得 MBA，所以他们不是 MBA。他们被识别为什么？如果他们不获得 MBA，他们被识别为什么？雇主认为非 MBA 是什么？差劲，好的？所以如果他们偏离，那么雇主认为他们是差劲的，即使他们在桌上跳舞说他们是优秀的。他们实际上是差劲的。他们被识别为差劲。所以他们的收益是什么？他们将获得什么报酬？他们将获得 30。

[段 36]

And sure enough, 35 is bigger than 30, so they’re not going to want to deviate. All right, so that’s good news. What about the bad workers? Let’s check them. So the bad workers, in equilibrium, they’re not MBAs. They don’t get an MBA. they’re identified as bad, and they’re paid what? What are they paid, these bad workers? Somebody? They’re paid 30, right? They’re paid their productivity, so their payoff is just 30. They didn’t get an education, so it was free. They get 30 for free, so their payoff is just 30. If they deviate, if the bad workers deviate, then they get an MBA so here come the bad workers andget an MBA so here come the bad workers they find their way into my class and SOM they have a miserable time I have a miserable time because they’re having a miserable time but at the end of the day they’re identified as good workers that entire is good workers and hence they’re paid 50 and their payoff is 50 minus 3 times 10.01, 10 and a penny, which is approximately 20. Is that right? So they don’t want to deviate either. And now I’ve done, now I’m done, I’ve shown it’s an equilibrium. So just to recap, to show that this was an equilibrium, I had to show that the good workers happily self-select into education and don’t want to deviate and skip business school.

[译文 36]

而果然，35 大于 30，所以他们不会想要偏离。好的，这是好消息。差劲工人呢？让我们检查他们。所以差劲工人在均衡中，他们不是 MBA。他们不获得 MBA。他们被识别为差劲，他们获得什么报酬？这些差劲工人获得什么报酬？有人吗？他们获得 30，对吧？他们按生产力获得报酬，所以他们的收益就是 30。他们没有接受教育，所以是免费的。他们免费获得 30，所以他们的收益就是 30。如果他们偏离，如果差劲工人偏离，那么他们获得 MBA 所以这里差劲工人来了获得 MBA 所以这里差劲工人来了他们找到进入我的课堂的路他们过得很悲惨我过得很悲惨因为他们过得很悲惨，但归根结底他们被识别为优秀工人那整个是优秀工人因此他们获得 50 的报酬，而他们的收益是 50 减去 3 乘以 10.01，10 加一分钱，大约是 20。对吧？所以他们也不会想要偏离。而现在我完成了，现在我完成了，我已经证明这是一个均衡。所以回顾一下，为了证明这是一个均衡，我必须证明优秀工人愉快地自我选择进入教育，不想偏离并跳过商学院。

[段 37]

I have to show that the bad workers self-select into not getting an education and don’t want to deviate and become MBAs. And I have to show that the employers infer from this what they should infer from this, which was fine. So I’m done. This is indeed an equilibrium. alright so notice in this equilibrium the good workers do manage to distinguish themselves from the bad workers and they do end up getting paid more albeit at the cost that they’re going to die a year later alright so thisthey’re going to die a year later. So this is called a separating equilibrium. Which I can never spell. I’m trying to spell this wrong. Never mind. It’s a separating equilibrium. Why is it called a separating equilibrium? It’s called a separating equilibrium because the types manage to separate and get identified. that’s slightly misleading the good types manage to separate and get identified and the bad types they don’t want to get separated but they do get separated alright now how many of you have seen some version of the Spence model before some of you right let’s go into this in a little bit more detail to see if we’ve really understood it okay so in particular in particular, could we get away with a shorter degree? Here we had people going to get MBAs, and it took them three years each.

[译文 37]

我必须证明低素质工人会自我选择不接受教育，不想偏离常规去读MBA。我还必须证明雇主会据此得出他们应该得出的推断，这没问题。所以我说完了。这确实是一个均衡。好的，注意在这个均衡中，高素质工人确实成功地与低素质工人区分开来，他们最终确实获得了更高的报酬，尽管代价是他们会在一年后死去，好的，他们会在一年后死去。这叫做分离均衡。我从来拼不对这个词。我故意把它拼错。别在意。这叫做分离均衡。为什么叫分离均衡？因为不同类型的人成功地分离开来并被识别出来。这说法稍微有点误导。高素质类型成功地分离开来并被识别，而低素质类型虽然不想被分离，但他们确实被分离了。好的，你们中有多少人在之前见过斯宾塞模型的某个版本？有几个是吧。让我们更详细地进入这个模型，看看我们是否真正理解它了。所以特别是，特别是，我们能否用一个更短的学位？这里人们去读MBA，每个人需要三年。

[段 38]

That seems an awful long time to get an MBA. So how about a 1-year?how about a one-year MBA? And some of you might think this is just some abstract example, but actually this is the kind of thing you hear about all the time. If you listen to ads in the education press, you keep on hearing schools, perhaps schools who lack economics professors, putting up proposals for one-year MBA degrees. I won’t mention any schools by name because I’ll probably get in trouble. So how about a one-year MBA? Let’s see if that will work and will allow good workers to separate themselves from bad workers. Let’s assume that the costs per year are the same as they were before. And let’s suppose that this candidate equilibrium, this putative equilibrium, involves the good workers getting the MBAs, the bad workers not getting an MBA, and the employers, just as before, identifying MBAs as good and non-MBAs as bad. Question, is that an equilibrium? Is that an equilibrium? So who thinks yes? Who thinks no? All right, so you can all tell me why then. So the answer is no. So why is that not an equilibrium? Why is that not an equilibrium? Somebody? Anybody? Why is that not an equilibrium? Someone hasn’t answered yet today. Yeah, here we go. So your name is? Osmond shout out shout out louder the bad workers wouldShout out?

[译文 38]

读MBA花三年时间似乎太长了。那一年怎么样？一年制MBA怎么样？你们有些人可能认为这只是抽象的例子，但实际上这是你经常听到的那种东西。如果你听教育广告，你会不断听到一些学校，也许是缺乏经济学教授的学校，提出一年制MBA学位的建议。我不会提任何学校的名字，因为我可能会惹上麻烦。那一年制MBA怎么样？让我们看看这是否可行，是否能让高素质工人与低素质工人分离开来。让我们假设每年的成本与之前相同。假设这个候选均衡，这个假设的均衡，包括高素质工人获得MBA，低素质工人不获得MBA，雇主和之前一样，将MBA识别为高素质，非MBA识别为低素质。问题来了，这是一个均衡吗？这是一个均衡吗？谁认为是？谁能告诉我为什么？好的，你们都能告诉我原因。所以答案是不是。那么为什么这不是一个均衡？为什么这不是一个均衡？有人吗？谁？为什么这不是一个均衡？今天还没人回答过。对，来吧。你叫什么名字？奥斯蒙德，大声点大声点，低素质工人会——大声点？

[段 39]

Louder? The bad workers would also benefit from doing the MBA because their payoff is still greater. Good, good. So what’s wrong in this equilibrium, it’s not the employer’s beliefs. If in fact people did follow this behavior, then employers would be right to identify MBAs with good. It’s also not the good workers’ problem. If in fact employers are going to pay more to MBAs, then the good workers are even more so going to want to go ahead and get MBAs. The problem here, this is not an equilibrium. It’s not an equilibrium, and the problem is the bad workers. The bad workers’ incentives are wrong here. Why? Because if the bad workers do what they’re supposed to do in this equilibrium, in this equilibrium, actually it isn’t an equilibrium, but in the supposed equilibrium, what they’re supposed to do is not get an MBA and get a payoff of 30. But if they went and got an MBA, if they deviate, if they deviate and no one else deviates, just them deviating, if they deviate, they get an MBA. according to the equilibrium they’re now identified as good workers, they’re identified as good, and so their payoff would be 50 minus one year and approximately 10 for a total payoff of 40, but 40 is higher than 30, so that’s violated our equilibrium condition. Everyone see that?

[译文 39]

大声点？低素质工人如果读MBA也会受益，因为他们的收益仍然更高。好的，好的。那么这个均衡的问题出在哪里，不是雇主的信念。如果人们确实遵循这种行为，那么雇主正确地将MBA识别为高素质是对的。也不是高素质工人的问题。如果雇主确实会付更多钱给MBA，那么高素质工人更会想去读MBA。这里的问题是，这不是均衡。这不是均衡，问题出在低素质工人。低素质工人的激励在这里是错误的。为什么？因为如果低素质工人在这个均衡中做他们应该做的事，在这个均衡中，实际上这不是均衡，但在假设的均衡中，他们应该做的事是不读MBA并获得30的收益。但如果他们去读MBA，如果他们偏离，如果他们偏离而没有其他人偏离，只有他们一个人偏离，如果他们偏离，他们会获得MBA。按照均衡，他们现在被识别为高素质工人，他们被识别为高素质，所以他们的收益会是50减去一年大约10，总收益为40，但40高于30，所以这违反了我们的均衡条件。大家都明白了吗？

[段 40]

So here, the bad workers, If it only took one year of pain and suffering to get an MBA, the bad workers would go and get an MBA as well, and that would be trouble because now everyone gets an MBA and it’s just like dancing on the table again. So how long must an MBA be? In this model with this cost structure, how many years must it take to get an MBA? Two years, right? One year didn’t work, but you can try at home and check that a two-year MBA will work. Two years will be just enough to put off the bad workers. Leaving aside the numbers, though, what’s the idea here? The idea is that to work as a successful signal, The signal has to separate the good workers from the bad workers. The workers have to choose to be separated. They have to self-select into being empowered.separated. They have to self-select into being MBAs or not being MBAs. And we need just enough pain and suffering, and let’s be careful, just enough difference in pain and suffering for the workers to select correctly. All right? So what we need, what we need, we need enough difference difference in cost for good workers to get the degree and for bad workers not to want to do so. So one thing we could do is have a two-year degree.

[译文 40]

在这里，低素质工人，如果读MBA只需要一年的痛苦和付出，低素质工人也会去读MBA，这将是个麻烦，因为现在每个人都会读MBA，这就像又回到在桌子上跳舞了。那么MBA必须读多长时间？在这个模型中，在这个成本结构下，读MBA必须花多少年？两年，对吧？一年不行，但你可以回家试试，检验一下两年制MBA是可行的。两年刚好足以阻止低素质工人。不过先抛开数字不谈，这里的想法是什么？这里的想法是，要成为一个成功的信号，信号必须将高素质工人与低素质工人分离开来。工人必须选择被分离。他们必须自我选择成为被分离的人。他们必须自我选择成为MBA或不成MBA。而我们需要足够的痛苦和付出，注意，是恰到好处的痛苦和付出差异，让工人做出正确的选择。好的？所以我们需要的，我们需要的是足够大的成本差异，让高素质工人获得学位而低素质工人不想去读。我们可以做的一件事是设置两年制学位。

[段 41]

How else, if you absolutely insisted on having a one-year degree, how could you create a difference in costs that would work? Suppose you were employed to advise some university out in the West somewhere who wants to have a one-year degree program, all right? What should you do in that one-year degree program to make it work, to make it allow people to separate? Raising tuition isn’t going to work, because that’s the same for good and bad workers. You need a way to separate the good and bad workers. How are you going to do it? You’re going to make it really hard. If you want to have a one-year degree program, it’s got to be really hard. You’ve got to really jack up the difference between the good and the bad workers. So you need tothe difference between the good and the bad workers. So you need to hire professors who have really bad handwriting. Alright. Let’s try and take a step back from this model and see what works. See what we’ve learned here. Let’s just try and draw some lessons off this. And I want to draw two kinds of lessons. I want to draw lessons in general about what makes a good, what makes a successful signal in society. And then I want to draw lessons about education. So I want to start with some nerdy lessons about game theory, if you like.

[译文 41]

如果你们绝对坚持要一年制学位，还有什么其他方法可以创造有效的成本差异？假设你受雇为某个西部地区的大学提供咨询，他们想开设一年制学位项目，好的？你在这一年制学位项目中应该怎么做才能使其可行，让人们能够分离？提高学费不会起作用，因为这对高素质和低素质工人是一样的。你需要一种方法来分离高素质和低素质工人。你打算怎么做？你要让它真的很难。如果你想要一年制学位，它必须真的很难。你必须真的加大高素质和低素质工人之间的差异。所以你需要——高素质和低素质工人之间的差异。所以你需要雇佣字迹真的非常糟糕的教授。好的。让我们从这个模型中退后一步，看看什么有效。看看我们在这里学到了什么。让我们试着从中得出一些教训。我想得出两类教训。我想总体上得出关于什么构成一个好的、什么构成一个社会中成功的信号的教训。然后我想得出关于教育的教训。所以我想先从一些关于博弈论的学术性教训开始，如果你愿意的话。

[段 42]

And then I want to draw some more specific lessons about the education system. So the key lesson here is the lesson we just learned. The key lesson is to be a successful signal, to be able to separate types of people, you need there to be large differences in cost. alright so the first lesson is a good signal it isn’t that it has to be costly it’s that it has to be differentially costly alrightit has to be differentially costly. It needs to be differentially costly across types. And the reason is you want the types to self-select, so there better be differences in costs. Be a little bit careful here. You could have differences in benefits, but we’ll leave those costs for now. All right. That’s one lesson. All right. Now, what’s that telling us in this model? That’s telling us that if you make it very, very easy to obtain qualifications in the U.S. society, for example, if you lower the standards that you need to get a high school degree, and perhaps you lower the standards to get a college degree, I’m not saying that is happening, I don’t want to take a political position on this. In England that’s happening, I can do that. In England that seems to be happening. So you lower the standards it takes to get a high school certificate in England and then you perhaps lower the standards to get a college degree.

[译文 42]

然后我想得出一些更具体的关于教育体系的教训。所以关键的一课就是我们刚刚学到的那一课。关键的一课是，要成为一个成功的信号，要能够分离不同类型的人，你需要有很大的成本差异。好的，所以第一课是，一个好的信号不是它必须代价高昂，而是它必须差异性地代价高昂，对吧，它必须差异性地代价高昂。它需要在不同类型之间差异性地代价高昂。原因是你想要不同类型自我选择，所以最好有成本差异。这里要小心一点。你可以有收益差异，但我们先把这些成本问题放在一边。好的。这是一课。好的。那么这在模型中告诉我们什么？这告诉我们，如果你让获得资格变得非常非常容易，比如在美国社会，如果你降低获得高中学位的标准，也许你降低获得大学学位的标准，我不是说这正在发生，我不想在这件事上采取政治立场。在英格兰那正在发生，我可以这么说。在英格兰那似乎正在发生。所以你降低了在英格兰获得高中证书所需的标准，然后你也许降低了获得大学学位的标准。

[段 43]

What are you going to see happen? What are you going to see happen? You’re going to see qualification inflation. If you make it easy for everybody to get the first degree, the good workers are going to go on and have to get a second degree. If you make it easy to get the secondare going to go on and have to get a second degree. If you make it easy to get the second degree, they’re going to go on and get the third degree. So what this model predicts is if you get rid of this cost difference, then workers will find a new way to raise the cost difference again. And the way that takes place, at least in some economies, is you start seeing qualification inflation. and by qualification inflation I mean that pretty soon even to drive a dump truck you need to have a university degree now what are the lessons here for education more generally This is a pretty sparse model of education but all of you and more immediately me are involved in the education system so we should care about it a bit It’s probably the most famous model of education as I say, it won somebody the Nobel Prize What is it telling us about education? So the first thing I claim that this is a rather pessimistic model of education.

[译文 43]

你会看到什么会发生？你会看到什么会发生？你会看到资格膨胀。如果你让每个人都很容易获得第一个学位，好的工人会继续并不得不获得第二个学位。如果你让获得第二个学位很容易，他们就会继续并获得第三个学位。所以这个模型预测，如果你消除了这种成本差异，工人就会找到新的方式来再次提高成本差异。至少在某些经济体中，这种方式的发生就是你会开始看到资格膨胀。我所说的资格膨胀是指，很快即使开翻斗车也需要有大学学位。现在这些对更广泛的教育有什么启示？这是个相当简陋的教育模型，但你们所有人，更直接地说我，都参与在教育系统中，所以我们应该关心它一点。这可能是最著名的教育模型，就像我说的，它为某人赢得了诺贝尔奖。它告诉我们关于教育的什么？所以我声称的第一件事是，这是一个相当悲观的教育模型。

[段 44]

Why is this a pessimistic model of education? What’s pessimistic about this model? Let’s talk about that a bit. Anybody? Some hands up. Some different hands. Why is it?Anybody? Some hands up. Why is this a pessimistic model of education? Way, way over there. I’m going to get another part of the room. I’ll give the cameraman a workout anyway. All right. You won’t learn anything. The rule is that school is absolutely no value for education. Good, good. Shout that into the microphone if that was right. You don’t learn anything at school in this model. Right, right. This is a model with no learning. There’s no learning in this model. All right? In fact, people in this model go in with their productivities at 50 and 30, and they come out with their productivities at 50 and 30. Nothing you do at school enriches you or makes you more productive. That’s a pretty pessimistic lesson. Here we are in lecture number, what is this, lecture number 23 or something? And the message of this model is, you guys haven’t learned anything, you’ve just had a lot of pain and suffering. So there’s no learning in this model. There’s no learning. All right? Now I hope, I hope that’s not true as a model of education, right? I hope it’s not true that we only have pain, all right?

[译文 44]

为什么这是一个悲观的教育模型？这个模型有什么悲观的？让我们来谈谈。任何 人？有些人举手。一些不同的人举手。为什么？任何人？有些人举手。为什么这是一个悲观的教育模型？那边，很远。我要看看房间的另一部分。我要给摄影师一个工作机 会。好的。你什么都学不到。规则是学校对教育完全没有价值。好的，好的。如果那 是对的，就对着麦克风喊出来。在这个模型中，你在学校什么都学不到。对，对。这 是一个没有学习的模型。在这个模型中没有学习。好吗？事实上，人们在这个模型中 进入时他们的生产率是50和30，出来时他们的生产率还是50和30。你在学校做的任何 事情都不会丰富你或使你更有生产力。这是一个相当悲观的教训。我们现在在第几讲 ，这是什么，第23讲左右？这个模型的信息是，你们什么都没学到，你们只是经历了 很多痛苦和折磨。所以在这个模型中没有学习。没有学习。好吗？现在我希望，我希 望这不是教育的真实模型，对吗？我希望不是我们只有痛苦，对吗？

[段 45]

But nevertheless, let’s pretend it’s true, at least for now, and see where it takes us, all right? So a second observation of this model, if we believe this model of education in which you don’t learn anything, education is just being used by those people who are good anyway to separate from those people who were bad anyway, right? Thenbad anyway, then education in this model is socially wasteful. Why is education socially wasteful in this model? In what sense is it socially wasteful? Think of it from the point of view of an economist. In this model, the productivity of the workers doesn’t change because of education, but some resources were used, right, some resources were used by the good workers to get an education, right. At the end of the day the good workers are better off, the bad workers are worse off, all right, but that’s and employers are the same as they would have been otherwise, all right, but that’s just redistribution, right. There’s no product from education, right, but resources were wasted in education. That make sense? So in particular in our two-year equilibrium, in our three-year equilibrium, it was the good workers who went to college, or in this case went to business school, and they wasted three years at five apiece. So there’s a waste of 15, a waste of 10 in the two-year model.

[译文 45]

但不管怎样，让我们假设这是真的，至少目前是这样，看看它会把我们带到哪里， 对吗？所以这个模型的第二个观察，如果我们相信这个教育模型，在那里你什么都学 不到，教育只是被那些本来就优秀的人用来与那些本来就差的人分离开来，对吗？那 么教育在这个模型中是社会浪费的。为什么教育在这个模型中是社会浪费的？在什么 意义上它是社会浪费的？从经济学家的角度来思考。在这个模型中，工人的生产率不 会因为教育而改变，但是一些资源被使用了，对，一些资源被好的工人用来获得教育， 对。最终，好的工人处境更好，差的工人处境更差，对，但那是而且雇主和之前一样， 对，但那只是再分配，对。教育没有产出，对，但是资源在教育中被浪费了。这有道 理吗？所以特别是我们的两年均衡，我们的三年均衡，是好的工人去上大学，或者在 这个案例中去商学院，他们每人浪费了三年，每年五个单位。所以有一个15的浪费， 两年模型中有10的浪费。

[段 46]

According to this model, education is socially wasteful. How do we actually visualize that waste in society? So let’s take the model seriously. Where is that waste manifested in society? Where’s that waste manifested? Yeah. People in school are working. Yeah, so you guys…it yeah yeah so you guys aren’t working and where else is it matter you guys sitting here is part of the waste you should be out you know doing something else and where else is the waste me right right right you should take all your Yale professors stop using them as Yale professors and wasting those resources and have us go out until the fields all right drive taxes or something all right all right all right so there’s a social waste here right and What we should do is, according to this model, is we should send the professors to drive taxis. Or dump trucks, I guess. I’m not claiming we’d be good at driving dump trucks. Our comparative advantage is certainly in teaching classes rather than driving dump trucks. But it turns out in this model, teaching classes is a complete waste of time. And therefore you’re better off using those resources to drive dump trucks. Third, notice that in this model, the result of education is what? It’s good for the good workers. You guys manage to separate yourselves and get paid high wages.

[译文 46]

根据这个模型，教育是社会浪费的。我们如何在社会中实际看到那种浪费？让我们 认真对待这个模型。那个浪费在社会中表现在哪里？那个浪费表现在哪里？是的。在校 的人在工作。是的，所以你们……是的是的所以你们没有在工作，还有什么其他重要的， 你们坐在这里是浪费的一部分，你们应该出去你知道做其他事情，还有什么其他的浪费 我，对对对你应该带走你所有的耶鲁教授，停止使用他们作为耶鲁教授，浪费那些资源， 让我们出去到田里，对开出租车或其他什么，对对对的，所以这里有一个社会浪费，对， 根据这个模型，我们应该做的是，我们应该让教授们去开出租车。或者翻斗车，我想。 我不是说我们会很擅长开翻斗车。我们的比较优势肯定是在教学而不是开翻斗车。但 原来在这个模型中，教课是完全浪费时间。因此，你最好使用那些资源去开翻斗车。第 三，注意，在这个模型中，教育的结果是什么？对好的工人有好处。你们成功地与其他人 分离并获得高工资。

[段 47]

That’s nice for the Yale graduates here. But who are the losers in this model? Who are the losers? The bad workers. The 90% of workers in this economy who aren’t naturally gifted, who aren’t going to find education easy, They in this model end up being paid 30 without the education system. How much would they have been paid? 30%.the education system, how much would they have been paid? 32. All right? So this model increases inequality. In this model, education increases inequality, and it doesn’t increase inequality in a benign way, just by making the rich richer. It increases inequality by making the poor poorer. All right? Education, in this model, increases inequality. In this model, it actually hurts the poor. Now that strikes me as a pretty important lesson, actually. Again, I don’t think we should take this model too literally. In the real world, I at least hope that some of you are learning something at Yale. You’re looking at me extremely doubtfully that you could possibly be learning anything at Yale. So maybe you’re not, I don’t know. But in the real world, I’d like to believe people are learning something at Yale. But one of the things that’s going on in education, in addition to learning, one of the things is that you guys are separating yourselves and signaling to employers that you’re going to be good workers for them.

[译文 47]

这对这个这里的耶鲁毕业生来说很好。但是谁是这个模型中的失败者？谁是失败者？ 差的工人。这个经济中90%的工人，他们没有天赋，他们不会觉得教育容易，在这个模型 中他们最终在没有教育系统的情况下获得30的报酬。他们会得到多少报酬？30%。在教育 系统外，他们会得到多少报酬？32。对吧？所以这个模型增加了不平等。在这个模型中， 教育增加了不平等，而且它不是以良性方式增加不平等，只是让富人更富。它通过让穷人 更穷来增加不平等。对吧？教育，在这个模型中，增加了不平等。在这个模型中，它实际 上伤害了穷人。现在这对我来说是一个非常深刻的教训。再次，我认为我们不应该太字面地 看待这个模型。在现实世界中，我至少希望你们中的一些人在耶鲁学到了一些东西。你们极 其怀疑地看着我，觉得你们可能在耶鲁什么都学不到。所以也许你们没有，我不知道。但在 现实世界中，我愿意相信人们在耶鲁学到了一些东西。但是在教育中发生的事情，除了学习 之外，其中一件事是你们在将自己与他人分离，并向雇主发出信号，表明你将成为他们的好 员工。

[段 48]

As a consequence, that’s great for you, but someone else is being paid less. This, in fact, is an important lesson to hear in an election year. In every election year in America, I’ve been in a few election years in America now, there are two things that all politicians agree on, whether they’re far right or far left. All politicians agree on two things. They agree that two things are good. One, kissing babies. Two, they all want to be, quote, the education president. Is that right? All of them. Is that right? Now, as a parent of some babies, I’m not sure I want to have politicians kissing babies, but that’s for another day. All right? The point here is, what we’re learning… Don’t go yet, guys. What we’re learning here is that if education hurts the poor, maybe we shouldn’t be so keen to decide that we should subsidize the education sector itself. Although as an educator, I hope you don’t tell that to anybody. What’s the takeaway message of this model then? The takeaway message is for education to work as a signaling device, for education to generate a separating equilibrium, some children have to be left behind. All right? All right?

[译文 48]

结果是，这对你们来说很好，但其他人得到的报酬更少。事实上，这是一个在选举年要听到 的重要教训。在美国的每个选举年，我已经在美国经历了一些选举年，有两件事所有政治家都 同意，无论是极右还是极左。所有政治家都同意两件事。他们同意两件事情是好的。第一， 亲吻婴儿。第二，他们都想成为所谓的“教育总统”。对吗？他们所有人。对吗？现在， 作为一些婴儿的父母，我不确定我是否想让政治家亲吻婴儿，但那是另一回事。对吧？重点 是，我们正在学习的东西……别走，伙计们。我们在这里学到的是，如果教育伤害了穷人， 也许我们不应该那么热衷于决定我们应该补贴教育部门本身。虽然作为一个教育者，我希望 你不要告诉任何人。那么这个模型的主要信息是什么？主要信息是，为了让教育作为信号装置 工作，为了让教育产生分离均衡，一些孩子必须被留下。对吧？对吧？