与sungmoo商榷。
交易费用无论定性还是定量都非“超验”的,而且是可测的。张五常认为,“"Transaction costs" must be defined to be all the costs which do not exist in a Robinson Crusoe economy.”,也就是说,“交易费用”是制度成本,这一点也得到了科斯的完全赞同(Cheung),这是定性方面。定量方面,张五常认为,“"Transaction costs" thus broadly defined are huge indeed. Variations cover the incomes of lawyers,financial institutions, policemen, middlemen, entrepreneurs, managers, clerks, civil servants, ... just about all the conceivable costs in society except those associated with the physical processes ofproduction and transportation.”。关于可测性问题,张认为,“It has been argued that it is fruitless to study transaction costs, because it is frequently impossible to measure them. This view is wrong. Fundamentally, measurement involves an assignment of numbers for the purposes of ranking, and precision in measurement can only be judged by the extent of agreement among different observers. To say that cost is measurable, or measurable precisely, does not necessarily mean it is measurable in dollars and cents. If we are able to say, ceteris paribus, that a particular type of transaction cost is higher in Situation A t han in Situation B, and that different individuals consistently specify the same ranking whenever the two situations are observed, it would follow that transaction costs are measurable, at least at the margin. Testable propositions may then be obtained, and that is the important thing.”
经济学作为一门经验科学,当然要重视经验的重要,无论交易费用经济学还是其他经济学。从严格意义上来说,一切理论都是方法论(吴承明,2001),理论正确与否或正确的程度如何,需要经验来检验。这个方面最好看一下Friedman的“The Methodology of Positive Economics”(1953, in idem, Essays in Positive Economics, Chicago, University of Chicago Press, 3-43. )
其实,经济学作为经验科学,就是研究人类行为的,无论价值还是交易费用等,都是通过对人类的行为的观察来建立起来的。通过对人类选择这而不选择那建立起来了“价值”概念,通过人类在市场、企业和政府这些市场主体之间的选择观察而建立起了交易费用的概念。只有先验的人类行为,而没有先验的价值或交易费用。
交易费用理论作为经济理论的一个分支,也必须具有可反驳和可检验和性质。关于可检验性,这就是通过预测或已发生的实事来检验理论。其实,张五常说,早在1981年,他就通过交易费用的分析预测到中国要走资本主义道路,这个预测已经应验。在解释方面,Demsetz在其“Towards a Theory of Property Rights”(Demsetz, H. (1967), 57 American Economic Review, 347-359.)一文中已经用交易费用解释了产权的起源。交易费用理论不缺乏经验基础。