我研究的一个经济学领域就是机制设计 。 如果你喜欢经济学中的工程部分 ， 机制设计 。 第一个想法是设定目标 。 社会设定它想要实现的目标 ， 然后机制设计师先弄清楚这些目标是否可能实现 ， 以及他们是否能够想出一种机制 ， 一个能够通过机构解决这些目标的机制 。
Now the particular area of economics that I got into is what's called mechanism design. Mechanism design is, if you like the engineering part of economics. The idea is the first try to set goals. Society sets the goals that it would like to achieve. And then the mechanism designer figures out first whether those goals are possibly achievable or not and if they are achievable of how to come up with a mechanism where an institution which can solve those goals.
让我给你一个非常简单的例子 。 想象你是一个机制设计师 ， 你有一个蛋糕 ， 你想把它分给两个孩子 ， 鲍勃和爱丽丝 。 那你怎么能把蛋糕分了 ， 让每个孩子都认为他或她的那一块至少和其他孩子一样大？换句话说 ， 你要以公平的方式切蛋糕 。
Let me give you a very simple example. Imagine that you're the mechanism designer, and you've got a cake which you want to divide between two children, Bob and Alice. Well, how can you divide the cake so that each child thinks that his or her piece is at least as big as the other childs. In other words, you want to, you want to cut the cake in a fair way.
如果你知道孩子们对蛋糕的看法和你一样 ， 这个问题有一个简单的解决办法 ， 你可以直接切蛋糕 。 在你看来正好是一半 ， 然后给每个孩子一块 。 但问题是 ， 也许孩子们对蛋糕的看法和你不一样 。 你以为你把蛋糕切成了两半 ， 但是一个孩子认为另一个孩子的份更大 。
Well, if you know that the children see the cake the same way you do, there's a simple solution to this problem, you can just cut the cake exactly in half from your point of view and give each child one of the pieces. But the problem is that perhaps the children don't see the cake the same way that you do. You think you've cut the cake exactly in half. But one child thinks the other child's pieces bigger.
那么如何解决公平分配的问题呢？即使你不知道孩子们怎么看蛋糕 ， 这是机制设计的问题 。 其实有一个很简单的非常巧妙的解决方法 。 你能做的就是让一个孩子来切蛋糕 ， 但是让另一个孩子选择他自己拿的那一块 。 换句话说 ， 一个孩子切 ， 另一个孩子选择 。 让我们看看为什么这样可行 。 因为当第一个孩子切蛋糕的时候 ， 他会确保以某种方式做到这一点：即不管另一个孩子得到了什么 ， 切蛋糕的人要让他的那块蛋糕至少和那块一样大 。 换句话说 ， 他要把蛋糕切成两半 。 如果其中一块更大 ， 他知道另一个孩子会拿走那一块 ， 所以他会把蛋糕平均切成两半 ， 无论另一个孩子得到什么 ， 这仍然是等分 。 所以第一个孩子会让他的份至少和另一块一样大 。 因为他是那样切的 。 另一个拿蛋糕的孩子可以拿走他最喜欢的 ， 所以他会想让他的那一块至少和另一块一样大 。 这样问题就通过一点巧妙的方法解决了 。
So how can you solve this fair division problem? Even when you don't know how the children see the cake, that's the mechanism design question. Well, it turns out that there is a very simple but very ingenious solution to this problem. What you can do is to have one child cut the cake. But have the other child choose which of the two pieces that he takes for himself. In other words, one child cuts, the other chooses. and Let's see why this works. It works because when the first child is cutting the cake. He will make sure that he does so in a way, that which ever piece the other child gets, the cake cutter thinks that his piece is at least as big as that piece. In other words, he's going to cut the cake exactly in half. If one of the pieces is bigger, he knows the other child is going to take that one. So he will cut the cake exactly in half. So whichever piece the other child gets, it's still an equal split. So the first child will think that his pieces at least as big as the others. Because he cuts it that way. And the other child, the one who takes the piece can take his favorite piece. And so he too will think that his piece is at least as big as the other. So the problem is solved with using a little ingenuity.