我与其他6个人合住在一间学生公寓里。我们都喝牛奶，有人喝得多，有人喝得少。但在我们之中只有3个人买牛奶，而且我们买的是3种不同的牛奶。这就意味着，我喜欢的那种牛奶可能很快就被喝光了。

I live in a student house with six others. All of us drink milk, some a lot, and some a little. Only three of us buy milk, and we buy three different varieties, meaning my preferred type can quickly run out.

更糟糕的是，我买的半脱脂牛奶似乎是其他所有人第二偏爱的品种。

Worse, my variety (semi-skimmed) seems to be the second preference of everyone else.

免费搭车现象很常见，而我也不想让严格的规定和强制机制来破坏宿舍里的和谐气氛。您有什么高招建议吗？

Free riding is common, but I don't want to spoil the atmosphere with strict rules and enforcement mechanisms¹. What course of action would you recommend?

哈康(Haakon), 来自牛津

Haakon, Oxford²


亲爱的哈康：

Dear Haakon,

显然，你认为人们永远不会自愿分摊自己应付的牛奶账单，而且认为建立必要的监控系统以确保行为合规又很费力。这说明你对经济理论的认识还很肤浅，因为，即使是理性的经济行为主体，也能从诚实行为中获得效用。因此，我们可以借鉴别人的经验，看看你可以怎么做。

You clearly think that people would never volunteer their fair share of the milk bill, and that the monitoring systems necessary to ensure compliance³ would be onerous⁴. This is a naive⁵ reading of economic theory, because even rational economic agents can gain utility from acting⁶ honestly. Your course of action therefore needs to be identified empirically.

被称为"面包人"的保罗oF (Paul F.)可以给我们一些启示。他是一个已经退休的经济学家，现在经营着一家给写字楼送面包圈的公司。他建立了一个信誉制度，由人们自行取走面包圈，并自行留下买面包圈的钱。

Draw inspiration from Paul F., also known as "the bagel man". Paul F. is a retired⁷ economist⁸ who now runs a bagel delivery business to offices. He operates an honour system, where people take bagels and leave the cash to pay for them.

保罗oF保留着所有客户付款比率的详细记录，并与《趣味经济学》(Freakonomics)一书的作者史蒂文o莱维特(Steven Levitt)和斯蒂芬o杜布纳(Stephen Dubner)分享了这些信息。

Paul F. keeps scrupulous⁹ records about the payment rates of all his clients, and shared them with Steven Levitt and Stephen Dubner, the authors of Freakonomics.

你或许可以简简单单地设立一个捐款箱，以便你的室友在偷喝你的牛奶时投进几个便士。保罗oF发现，这个机制可以实现89%的付款率。令人更加欣慰的是，他发现，在小写字楼工作的人更诚实，在他自己工作的地方也一样。

Perhaps you should simply leave a contribution box to make it easy for your housemates to contribute a few pennies as they swipe your milk. Paul F. found that this system produced a payment rate of 89 per cent. Even better, he saw more honesty in small offices, and in the office where he himself worked.

学生宿舍的情况可能类似。
A student house is probably similar.

但在一些重要时刻，例如圣诞节期间，人们的诚实度可能会降低--因此，在考试期间，最好还是看护好你的捐款箱。

Honesty only broke down at times of stress, such as Christmas - so guard the box in exam season.