因为一门课程的原因，我写了一段关于硕士论文（现在是一篇working paper)内容的简单陈述。目标就是让受过大学本科教育的人都能够看懂。所以请各位指正啦，帮忙看看哪里写得很confusing的~

Have you ever worked with classmates who never spend a second on the team assignment? Or have you lived with roommates who never clean the house, but instead always count on you to do the job? Those people are called “free riders”, for they consume more than their fair share of a public good (such as a clean kitchen which every house member can use). A big problem generates by free riders is loss of efficiency for the society as a whole. That is why economists, who value efficiency, try their best to find out the most effective mechanism in promoting cooperation and decrease free-riding problem.

One research tool economists refer to is lab experiment, in particular, an experiment called public goods game (PGG). In a public goods game, every player in a group secretly and simultaneously chooses how much of their own experimental money to put into the public pot. The group as a whole does best when everyone contributes all of their money into the public pot. However, any player has the incentive to under contribute. This experiment nicely capture the free rider problem in real life: We will all be better-off if everyone cooperates, but some may have the incentive to hold back their effort.

Researchers have run hundreds of such experiments and do found that cooperation gradually decays when people play the game over and over again. Two researchers, Fehr and Gaechter, discovered a very effective way in preventing the decreasing contribution trend. They added an extra stage, named “punishment”, on top of the public good game. Here is how their game works. Players first played the standard public goods game described above. Then the experimenter provides every group member a list of everyone’s contribution. Based on this information, players can decide whether and how much to reduce the earnings of certain group members from the game. At the same time, however, the punisher has to bear a cost – for in reality, the behavior of punishment is often costly. In the experiment, the punisher’s earnings is reduced together with the punished. Fehr and Gaechter showed that even when people only play the game once and this costly punishment does not generate any future benefits, many are still willing to punish free riders at their own cost.

However, in real life, people are heterogeneous so that their ability to contribute varies from one to another. Imagine that two students, Tom and Mike, are working together for a computer programming project. If they are equally capable, it is very easy for them to split the task. Now suppose Tom can do the task ten times as fast as Mike. Since their productivities very so significantly, they may have different opinions on the “appropriate” contribution level to the project. Mike might think that Tom should do the job since he is an expert, but Tom might think that it is totally unfair for Mike to free ride on him. It that case, it is unclear who should is the one to be blamed if the project fails to due on time.

In this paper with Charles Noussair, we aim at investigating how people decide on punishment mechanism in this kind of situation. In particular, we let players choose the punishment rules, and exam whether these rules selected remain efficient comparing with the previous literature.

The main features of our experiments are as follows. We randomly assign players into groups of four, and different roles. Two members of a group are “capable” players, and the rest two are “weak” players. Given the same amount of contribution, everyone benefits more from capable players. For every several periods, they can express their preferences of the following punishment rules: I allow “capable players” to be punished if they under contribute / I allow “weak players” to be punished if they under contribute/ I allow “capable players” to be punished if they over contribute / I allow “weak players” to be punished if they over contribute. If more members say “yes” than “no” vote to a certain item, this punishment rule will be executed for the following number of votes before the next voting is carried out.

The main result we find is that punishment rule chosen by a mixture of capable/ weak players are not as efficient as the rule chosen b a group of players with the same ability. The reason lies in the fact that players are more likely to vote for allowing punishment of another type rather than their own. This mirrors the reality in that institutional rules may not be efficient as they should be if it is voted out by heterogeneous people who have different belief of the contributions other society members should make.

Along the way you bump into people who make a dent on your life. Some people get struck by lightning. Some are born to sit by a river. Some have an ear for music. Some are artists. Some swim the English Channel. Some know buttons. Some know Shakespeare. Some are mothers. And some people can dance ...

You can be mad as a mad dog at the way things went; you can swear and curse the fates – but when it comes to the end, you have to let go.

昨天看到好友Arthur的一篇blog，写得很朴实，但不知道怎么看后很受震动。我前篇博客写到的“社会价值观的重大缺失”，这篇文章就提供了一个很好的例子。人们写blog虽然经常是信手拈来，不经修饰，但正是这样的文字最能够反映一个人的精神状态。Arthur是一个很虔诚的基督徒，阅读他的文字经常能够强烈感受到一种超越这个功利世俗，物欲横流社会的信仰的力量。也许这样理想主义的文字，在当今媒体（杂文版）已经不多见了。诚然如穆梵同学所说，我并没有什么资格评判现在人们追求幸福的方式，因为我应该尊重每个人追求幸福的标准和手段。中国人多，这既是我们比较优势的来源，也是一种诅咒：因为追求物质利益最大化的过程中，竞争压力比人力稀缺的西方社会激烈这是在所难免的。但我以为每个人在自己的效用函数中多加入一点比如分享的快乐，社会的责任，理解与宽容；人们对“幸福”的定义和追求手段就会多元化一点，竞争的压力可能也会由此少一点。
 
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最近在跟一位澳大利亚的老师学习希腊文。除了买一些基本的书本之外，他几乎是0成本地教我。上他的课轻松愉快而且知识含量丰富，真的是很有趣的一件事情。我问他为什么他愿意从自己的工作中抽时间出来教我，他说，the joy comes from sharing. 我认真地看着他，微笑着点了点头。我认同他的观点是因为我自己的体验也是这样。我最快乐的时候之一是把自己的买的好东西拿出来大家一起吃；自己学到的一些技能拿出来服务别人；还有把成功和不成功的经验拿出来分享..... 虽然我承认我也追求认同感，其中有时候也包括虚荣心和好为人师的部分，但真正喜乐是来自很单纯的泉源---一种快乐变成很多分的过程。
 
我们的社会也因为分享而变得更加紧密联系。现在流行的wikipedia, wikibooks就是群体协作和分享的杰出代表。我在美国上过的几门课，老师就通过自己和别人协同撰写的wiki books来作为教材。这不仅是一种免费的资源，而且学生也可以参与贡献智慧。我以前在圣塔非学校的老师Dave Feldman后来开过一门introductory complex networks的课程，里面要求学生通过写博客的方式来做作业；课堂的案例讨论更是直接从学生的阅读日志中来。
 
不知道谁说过这么一句话，一种新的媒介往往带来一种新的社会变革。我是非常赞同的。而其根本的原因之一，我以为，是人类心灵深处愿意分享的动力，而这样一种快乐是无法用金钱来换取的。从我自己的经历来看，我觉得中国的基础教育最忽视的就是教学生如何去合作和分享。从小学一直到大学，我们往往学会了充满竞争和彼此敌视的心态和各自为阵的打法，却不知道如何去 be interdependent，在社会这个大机器里发挥各自的长处去做更大更宏伟的事业。
 
所以新的一年，希望自己可以继续不断地学习新的知识，多走一些地方，然后分享给更多的人。