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(转)谈谈著名经济学家张五常教授的学术贡献及其局限性

已有 627 次阅读2016-4-27 18:35 |个人分类:转来的| 经济学家, 张五常, 局限性

谈谈著名经济学家张五常教授的学术贡献及其局限性

Professor Steven Cheung’s academic achievements and limits

   邀请世界著名经济学家张五常教授来做报告告诫经济学专业的学生“经济学是失败的,讲授主流经济学的经济学教授是废物,经济学院同事们的这种勇气和坦诚令人赞赏。商学院微信公众号的编辑找我写一点上周张五常教授讲座的评论,我答应写个短评谈谈著名经济学家张五常教授的学术贡献和局限性。实际上我从未读过张教授的任何学术专著或者学术杂志研究论文,我知道的所有关于张教授的事情都来自他过去的公共演讲。“一叶知秋”,我觉得从张教授的各种演讲中可以得到对张教授工作相当好的了解。

   张教授是一个洞察力深刻,能够直接看到经济学问题核心的天才,同时他也非常执着地相信现实事物必然是合理的和有效率的,其存在必有一个简单的理性解释。这种对简明和现实理性的强烈信念非常符合中国哲学中“大道至简”的观点。在自然科学界,我们常说“好的科学必然是简单的科学”。如果一个科学理论复杂到让人难以理解,这个理论错误的可能性就很大。不幸的是,当前的科学工作者往往忘记了这一点,制造出了越来越复杂和稀奇古怪的理论。

   张教授的佃农理论很好地体现了这种对简洁和现实合理性的信念。当佃农从地主那里租来一块田地,他们之间应该怎样分割农田的收成/收入?从当时主流经济学的观点来看,地主应该在支付农民及其农具的边际产品后获得农田的所有剩余收成/收入;或者,地主应该收取农田的边际产品,而农民得到所有剩余收成/收入。但实际上,在台湾和东亚其他地区,地主收取固定比例的地租,这与主流经济学理论的预言完全不同。因此,主流经济学家认为现实存在的这种收入分配合同是不合理和低效率的。张教授拒绝接受这种教条观点,他提出了一个证明其合理性的解释。因为测定劳动者和土地的边际产品与监督劳动者的努力程度或者不太可能或者成本太高,所以信息不确定性导致地主按比例收租,这种租地合同在信息不确定性的条件下是合理的和有效率的。张教授的这一工作是信息不对称经济学的开创性发现,约瑟夫·斯蒂格利茨在这一发现的基础上开始了他的诺贝尔获奖工作(2001年度诺贝尔经济奖)。

   张教授此后工作也都表现出这种对现存事物的合理性的强烈信念,就像在佃农理论中表现出来的一样。他直接观察经济现象,把它们与主流经济学的预言相比较,然后从信息不对称、交易成本或现实世界的考虑出发给出更合理、可能也更正确的解释。例如,他对影剧院里最好座位的票相对便宜、先被卖完的解释。后来获得1991年度诺贝尔经济奖的罗纳德·科斯,特别欣赏他的工作并大力扶持。张教授的这些突出贡献使他成为新制度经济学发展中的一个重要人物。他对现实事物的合理性及效率的强烈信念,使他极力反对政府除维持法律秩序外对经济的任何干预。

   张教授是主流经济学及其对现实世界问题教条态度的激烈批评者。他认为,经济学在处理现实世界问题上是彻底失败的,经济学应该是实证科学。华人经济学家经常误用汉语“实证一词,张教授也不例外。哲学上实证的英语是实证主义的Positive, 而不是empirical(经验的)。大多数华人经济学家把empirical 误译为实证。我觉得张教授所说的实证,不过是指以证据为基础得出研究结论。我完全同意他这方面的观点,并且认为经济学几乎从一开始就走上了一条错误的发展道路。作为经验科学,经济学应该以物理学或者生物学为榜样,从观察现实世界得到关于现实世界的结论。我也完全赞同张教授对学术界过分强调一流杂志文章发表数量的批评。我一直认为研究论文的价值在于文章本身内在的价值,而不是发表杂志的影响因子。

   超人的才华既可以是让人在学术天空翱翔的翅膀,有时也可以成为阻碍人进步的尾巴,这样其主要用处就变成让人翘尾巴。张教授的过人才华和对简洁的强烈信念也带来了他自身的局限。因为他早期事业的成功以及他的个性,张教授对自身信心十足,瞧不起从事主流研究的经济学同行。他看不出自己数学和抽象理论化的能力不足是弱点,这个弱点使他失去获得诺贝尔奖的机会,反而极力贬低数理经济学和使用数学方法的经济学家。他倡导经验(实证)经济学,却认识不到数学在经济学的应用极大地促进了经济学的经验研究。如果他早年认识到自己的弱点并且与数学能力强的经济学家合作,他很有可能已经分享到了诺贝尔奖。因为他数学不强,他不懂得数学作为公理体系不需要现实世界的验证。他错误地把不需要客观世界验证的公理体系例如数学与需要客观世界验证的实验/经验科学如物理学和生物学混为一谈,作为他所谓的公理性科学。

   张教授对于主流教条的执着反对好像已成为他本身的教条,使他看不见经济学的大画面。与他的经济学是失败的,经济学家是废物的断言相反,经济学实际上非常成功地提出了成本效益分析、稀缺资源最优化分配和限制条件下的优化等重要方法和思路。经济学可能太成功了,因为这些方法与思路影响了和渗透到了人类社会的各行各业,以至于人们不再认为这些经济学方法和思路是经济学。任何科学都有其未解决的问题,任何科学都有其错误但时髦的理论,经济学也不例外。

   所有经济学概念和结论都有其限制条件和适用范围,即便是张教授大力推崇的需求定律也不例外。当价格下降时,需求增加这一关系主要适用于对消费需求的静态比较分析,并且需要消费者没有战略行为。当做动态分析时和分析投资物品时,这一定律可能就不再正确。当我教微观经济学,告诉学生现实世界不存在吉芬物品时,有些学生认为中国的房屋需求随房价上升而增加可以作为吉芬物品的例子,还有黄金也随价格上升而需求增长。实际上,张教授在讲座中也承认需求定律的正确性依赖于正确选择让哪些别的变量恒定和让哪些别的变量变化。如果是这样,被张教授当作垃圾的经济学定理与被他推崇为经济学唯一正确的需求定律之间的差别不过是五十步与一百步之间的差别。

   根据张教授自己所述,他至少有40多年不读经济学期刊的文章了,因为他认为这些文章完全无用。这一点显示了过人的才华和早期事业的顺利可能成为其后人生事业的负担。乔治·阿克尔洛夫的诺贝尔获奖文章《柠檬(劣质二手车)市场》曾被三种期刊拒稿。头两种期刊拒绝将他的文章送审,并且告诉阿克尔洛夫,他们的杂志不发表这样肤浅的文章。第三种杂志的审稿人表示如果阿科尔洛夫的文章正确,整个经济学就会是错误的。张教授发表《佃农理论》好像比阿克尔洛夫发表《柠檬市场》顺利得多(不过《柠檬市场》投稿被拒的都是经济学最高水平的杂志)。因为张教授从很早之前就已经不再读新发表的经济学论文了,他好像不知道神经经济学可能已经找到测量效用和其他主观变量的代理指标。经济学在过去50年的实际进步超过了张教授自身的进步,也超过了张教授感受到的经济学进步,而张教授为经济学的这些进步做出了重要贡献。我们需要向张教授学习的是他挑战主流经济学、开创新研究领域的勇气和智慧。至于他在演讲中的具体言论和对人对事的具体评论,我们姑且听之,不必过分认真,也可以当成娱乐。

   Our colleagues in the school of economics should be commended for their courage and frankness in inviting a world renowned economist to tell their economics students that economics is a failed knowledge and economics professors doing mainstream economics are “feiwu” (废物,good-for-nothing). When NUBS Wechat editors asked me to write something about Professor Steven Cheung’s lecture last Wednesday, I agreed to write a short comment on his academic achievements and limits. Actually I haven’t read any books or academic journal papers by Professor Cheung, and all I have read are his often self-promoting public speeches. As the Chinese phrase (that people can) “tell the arrival of autumn from one leaf”, I feel that I have got a pretty good idea of Professor Cheung’s achievements and limits from his public speeches.

Professor Cheung is a genius with extraordinary insight that cuts directly into the coreof economic phenomena as well as a powerful single-minded belief that all things that exist must have a simple explanation from rationality and efficiency. This belief resonates well with the Chinese philosophical saying“the greatest understanding is via the utmost simplicity”. In natural science,we used to say “good science is simple science”; if a scientific theory is too complicated for people to comprehend, it is most likely to be wrong.Unfortunately, scientists nowadays seem to have forgotten this and build more and more complicated or outlandish theories.

This belief in simplicity and rationality of reality is well demonstrated in his theory of shared tenancy. When a tenant farmer rents a piece of farmland from a landlord, how should they share the output/revenue of land? From the viewpoint of the mainstream economics at the time, the landlord should pay the marginal products of the tenant farmer and his tools and then keep all the remaining output/revenue;or the landlord should charge the marginal products of the land and the tenant farmer keeps the remaining output/revenue. In reality, the tenancy contracts in Taiwan and many East Asian economies tend to be that the landlord takes a fixed proportion of the output/revenue, contrary to the conclusion of the mainstream economics. So many economists at the time considered shared tenancy is not a rational or efficient decision. Professor Cheung rejected such a dogmatic view and provided an analysis of its rationality: it’s impossible or too costly to find out the marginal products of the tenant farmer or the land, or to monitor the efforts of the tenant farmer. Because of the information uncertainty, shared tenancy is a rational and efficient decision. This is a pioneering finding in economics of information asymmetry, from which Joseph Stiglitz started his Nobel Prize (2001) winning work.

Later works by Professor Cheung all share this strong belief in the rationality of existing phenomena exemplified by the theory of shared tenancy. He made direction observations of phenomena and compared them with the predictions of mainstream economics and then gave a better and probably correct solution based on information asymmetry, transaction costs, or real world considerations (for example, the reason that the best seats in theatres are relatively cheaper). His works were particularly appreciated and promoted by Ronald Coase who later received Nobel Prize for Economics (1991). These outstanding works made him a key figure in the development of new institutional economics. Because of his strong belief in the rationality and efficiency of all that exist, he objects vehemently to government intervention except maintaining law and order.

Professor Cheung is a vocal critic of the mainstream economics and its dogmatic approaches toward real world issues. To him, economics has failed to solve real world issues and economics should be a “shi zheng” (实证) science. Chinese economists tend to misuse the term “shi zheng” (实证)  and so does he. In philosophy, positive in the sense of positivism is translated into “shi zheng” (实证), whereas empirical is “jing yan”(经验). Most Chinese economists incorrectly translate empirical into “shi zheng” (实证). In my view, when Professor Cheung talks about “shi zheng” (实证), he actually means evidence-based research (conclusion). I agree fully with his view, and I think that economics took a wrong path in its development almost from its very beginning. As an empirical science, economics should model itself in the tradition of physics or biology, drawing conclusions from observations of the real world. However, economics models itself in the image of mathematics and tries to derive conclusions from a few abstract axioms. I also fully agree with his criticism on the academic practice of overemphasis on (the number of top) journal publications. I always think that the value of a research paper lies with its intrinsic value rather than the impact factor (IF) of the journal in which it has been published.

Extraordinary talent can be the wings enabling a person to fly in academic sky, but at times it can also become too big a tail for someone, a burden for progress and good only for raising it up. Likewise, Professor Cheung’s talent and single-minded belief in simplicity also brew up his limits. Probably because of being extremely successful in his early career as well as his personality, Professor Cheung is very confident in himself and often looking down upon economists doing the orthodox economics. He could not see his lack of dexterity in mathematics and abstraction for theorization being a weakness, which cost him a Nobel Prize, and instead he belittles mathematical economics and economists using mathematical approaches. He promotes empirical economics, but fails to appreciate that application of mathematics has been the greatest facilitator of empirical research. Had he appreciated his weakness and collaborated with more mathematics minded economists, he might have had shared a Nobel Prize in Economics. Because of his weakness in mathematics, he does not understand that mathematics as an axiomatic system does not need confirmation from the real world. He is wrong in mixing up axiomatic systems such as mathematics with experimental/empirical sciences such as physics and biology which need confirmation from the real world.

Professor Cheung’s single-minded objection to the mainstream dogmas seems to have become a dogma of its own, which makes him unable to see the big picture of economics. Contrary to his assertion that “economics is failed and economists are good for nothing”, economics with its concepts of cost-benefit analysis, optimal allocation of scarce resources and optimization under constraints etc has been very successful. Probably too successful, people no longer consider them being economics, because economic thinking has influenced, and become part of, every walk of life. In any science discipline there are unsolved problems and fashionable theories that are actually wrong, which is exactly the reason why some people want to become academics, and economics is no exception.

All economics concepts and conclusions have their qualifiers and domains of definition, even for the demand law so much cherished by Professor Cheung, “when price decreases, demand increases”. This relation has its qualifiers, as it is true for comparative static analysis of consumption demand for people without strategic behaviors, but not necessarily for dynamic analysis and for investment goods. When I taught microeconomics and told students that Giffen goods do not exist in real world, some students objected by noting that the demand for houses in China and for gold on world market is increasing when price is increasing. Professor Cheung actually conceded in his talk that the validity of demand law depends on correctly allowing some other variables to change while keeping some other variables constant. From this concession, the difference between those axioms/theorems trashed by him and the demand law praised by him as the only true thing in economics is just one between fifty steps and one hundred steps.

According to Professor Cheung himself, he has not read economics journal papers for probably more than 40 years because he thought those papers useless, which shows how an extraordinary talent and easy success in early career can be a big burden. George Akerlof’s Nobel Prize winning paper “The market for lemons” was rejected by three journals in 1960s. Two journals refused to send his paper for review by telling Akerlof that they would not publish a paper of such triviality; and the third journal’s reviewers told him that if his paper was correct, the whole economics would be wrong. It seems that the road to the publication of Professor Cheung’s “Theory of sharedtenancy” was smoother than that of Akerlof’s “The market for lemons” (though the journals that rejected Akerlof’s paper are all top-class in economics). Because Professor Cheung no longer read economics papers since a long time ago, he does not appear to know that neuroeconomics probably has found measurable proxies for utility and other previously subjective quantities. Economics in the past 50 years has progressed more than Professor Cheung has progressed or he has been aware of. He actually contributed to this progress in economics. What we should learn from Professor Cheung is his courage and wisdom in challenging the mainstream economics dogmas and breaking new ground for economic research. His actual words and remarks in his lecture should be taken with a pinch of salt and for entertaining ourselves.




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