从历史的角度看待经济学理论和贫富差别– 谈谈托马斯·皮克迪的《21世纪的资本》

Capital in the twenty-first century by Thomas Piketty: a view of economic theories and inequality from the historical perspective

法国经济学家托马斯·皮克迪的《21世纪的资本》在2014年5月18日成为《纽约时报》非小说类畅销书第一名。虽然诺贝尔经济奖得主保罗·克鲁格曼大力推荐此书，但是经济学界主流对此书的评价不一，不少人把此书的成功归结为2008年金融危机导致的美国社会“仇富”心理。《21世纪的资本》法文原著在法国并没有成为畅销书，英译本在美国成为畅销书后，其影响“出口转内销”使法文原著成为法国畅销书。

在读此书之前，我看过一些反映主流观点的书评，因此也把此书视为左翼经济学家的异见之作。克鲁格曼近年的观点比较偏左，他大力推荐左翼异见也在情理之中。我在阅读过程中，得出与主流观点不同的对此书的看法。皮克迪认为经济学研究需要以更长的历史尺度为基础，这一观点很重要，经济学主流应该认真对待。皮克迪这本书为读者提供了一个与主流经济学不同的视角。

皮克迪在书中指出1）八十年代里根、撒切尔的保守主义革命并没有使美、英经济发展加快，而是过去发展速度远高于英美的德、法、日等国家的经济发展放慢了；2）1950-1970期间美、英实行高税收政策，经济发展比里根、撒切尔的低税收改革后快；3）从300年资料得到的结论与从30年、50年数据得到的结论非常不同，经济学主流过于依赖第一次世界大战后尤其是第二次世界大战后的资料；4）经济学还是称为政治经济学比较合适，因为经济学是社会科学的一部分，经济分析和经济政策与历史、文化、政治密不可分。

说到政治经济学，我记得萨缪尔森《经济学》第十版上说经济学又称政治经济学。实际上，人类社会很少纯粹由经济学解决的问题，政治权利/权力与经济利益纠缠不清。经济利益问题常常需要通过政治/政府干预得到解决，而政治权利/权力也经常会干预经济过程。用列宁的话说，政治是经济的集中表现。在马克思主义的政治经济学体系内，价值是社会必要劳动时间的体现。随着劳动生产率的提高，生产出工人生活必需物资所需的必要劳动时间越来越少，也就是说劳动力的生产成本越来越低。由于资本的贪婪本性，资本家只会付给工人劳动力的生产成本，而劳动力的生产成本越来越低。因此，工人必然日益贫困化。但是，工人运动和马克思主义影响下的社会主义政党使得工人绝对贫困化在政治上不可能。为避免资本与资本控制的政权在社会革命中一起灭亡，资本控制的政权不得不搞社会改良，增加社会福利，改善工人劳动条件和经济收入，马克思预言的工人贫困化也就落空了。经济问题不能不考虑政治生态，用在西方政治生态下发展完善的现代经济学来分析中国的经济问题，必须考虑到中国的政治生态，否则就会做出错误判断。

皮克迪通过对十八世纪以来法国及英国、美国、德国、日本等国财富及收入变化的研究发现：在市场制度下，财富会越来越集中于少数人手中。在第一次世界大战前夕，财富高度集中。两次世界大战及随后的政治、科技发展逆转了前期的财富集中过程。战争对社会财富有巨大的破坏作用，而财富的积累是一个相对缓慢的过程。因此，战争常常能缩小贫富之间的差距。战争期间负责任的政府会让富人贡献更多财富来支持国家的战争努力，采取相对减轻对穷人的压力的措施，以便做到全民动员。从二十世纪初到七十年代，是工人政党和左翼政党力量蓬勃发展的时期，其政治活动增加了工人的社会福利和经济收入，抑制了财富的集中。很多欧洲国家的社会党或工党在第一次或第二次世界大战后开始执政。美国的罗斯福政府也采取了大力干预经济的新政。凯恩斯主义经济学在二十世纪三十年代的出现也为左倾政府干预经济提供了理论基础。

随着工人运动影响在二十世纪七十年代开始的衰落，凯恩斯主义经济学在实践中也遇到“滞胀”困境，右倾的货币主义学派占据了经济学的统治地位。货币主义学派主张政府退出，让市场解决除维持法律秩序之外的一切问题。1980年以来的这些发展，重新启动了财富集中过程，21世纪初的财富集中程度正向一战前夕回归。这些变化说明，解决贫富差别过大不能只靠市场机制。第一次世界大战开始到二十世纪七十年代的贫富差距缩小不是市场机制完成的。皮克迪的这一工作是对库兹涅茨曲线（Kuznets curve）的否定。库兹涅茨曲线是由美国经济学家、1971年诺贝尔经济学奖得主西蒙·库兹涅茨在1953年提出来的收入分配状况随经济发展过程而变化的倒U字形曲线，即贫富收入差距随经济发展“先变大，后变小”。

经济学上的很多结论是从时间序列数据得出的。作为曾经长期从事生物医学实验的研究者，我很清楚生物医学研究者不会接受用单一个体时间序列得到的结论。例如给一个感冒发烧5天的病人吃一块糖，极有可能两天后病人就痊愈了。以经济学时间序列方法分析这一次感冒从开始到痊愈的过程，很可能得出是这块糖治好了病人的感冒。因此，生物医学研究只相信有随机对照组的结果。因为宏观经济分析经常依赖单一样本在不同时间点或不同样本在同一时间点的比较，基本上所有结果都缺乏生物医学研究意义上的对照组，所以，皮克迪强调短期结果不可靠、应该通过研究历史性长期资料来得到正确结果的观点对经济学研究具有重要意义。

Capital in the twenty-first century by French Economist Thomas Piketty became number one on The New York Times bestselling hardcover nonfiction li st dated 18 May 2014. Although the Nobel Prize in economics laureate American economist Paul Krugman recommends it enthusiastically, most mainstream economists are more reserved in their evaluation of this book. Quitea few commentators attribute its success to the concern over wealth and income inequality in the United States following the financial crisis in 2008. This book was not a bestseller in France when it was first published in French, but its English translation is a big success in the US. Its popularity in the US feeds back to France and makes it a bestseller there as well.

Before reading this book, I had read some book reviews from mainstream economists and because of their influence I thought the book just another work of left-wing dissidents. Krugman’s recent views have been leaning left, so it would be understandable that he recommends strongly a left-wing book. However, during reading this book, I got a very different view from those mainstream commentators on this book. Piketty thinks that economic research should be based on long historical date series, which is a very important view and should be treated seriously by the mainstream economics. Piketty’s book provides an angle different from those of mainstream economics.

Piketty points out in this book: 1) the conservative revolution started by Reagan and Mrs Thatcher during 1980s did not speed up the economic growth in the US and UK, it is the decreased growth rate in previously fast growing German, France and Japan that makes the US and UK appear to grow faster; 2) the US and UK implemented higher income tax rates during 1950-1970, but their economic growth rates then were higher than those after the Reagan’s and Thatcher’s low tax rate reforms; 3) conclusions drawn from data of 300 years could be very different from those obtained from analyzing data of 30 years or 50 years; 4) economics may be more appropriately called political economics, because economics is a part of social sciences and economic analysis and economic policy making are closely related to history, culture and politics.

Concerning political economics, I remember that Samuelson’s Economics 10^th edition says that economics is also called political economics. In fact, in human societies there are rarely issues that concern purely economics; political rights/powers are always entangled with economic rights/interests. Issues in economic interests are often solved by political/government intervention, while political rights/powers often interfere with economic processes. As Lenin said, politics is the concentrated manifestation of economic interests. In the system of Marxist political economics, value is measured by the socially necessary labour time. When labour productivity increases, the production of the goods needed for workers to maintain their capacity to work needs less necessary labour time, that is, the production cost of the capacity to work gets smaller and smaller. Because of the greedy nature of capital, the capitalists would only pay workers their production costs of the capacity to work, while the production cost of the capacity to work gets smaller and smaller. Therefore, workers would become more and more pauperized. However, the labour movement and the political parties under the influence of Marxism made the absolute pauperization of workers politically intangible. In order to avoid the destruction of capitalists together with the capital controlled government in a social revolution, the capital controlled government will start social reform, increase social welfare, improve working conditions and workers' incomes. Consequently Marx’s prediction of workers’ pauperization was not materialized. Dealing with economic issues must take the political framework into consideration. Using economics developed under the western political framework to analyze the economic issues in China must take China’s political framework into consideration. Otherwise, we may have wrong assessments on economic issues in China.

Via examining the changes of wealth and income in France, UK, USA, Germany and Japan, Piketty finds that wealth will be more and more concentrated in the hands of a few people under the market mechanisms. On the eve of world war one, wealth was highly concentrated, but the two world wars and subsequently changes in politics and science and technology reversed the earlier wealth concentration process. War is a great destructor of social wealth which is accumulated relatively slowly. So war is often able to reduce the difference between the rich and the poor. During a war, a responsible government usually asks the richer to contribute more wealth to the nation’s war efforts, while reducing relatively the burden of the poor so that the whole population can be mobilized to defend the nation. The period from the beginning of the 20^th century to the 1970s saw the thriving development of socialist and labour parties, whose policies tend to increase workers’ welfare and incomes and inhibit wealth concentration. The socialist parties or labour parties started to become the party in power after the First or the Second World War. In the United States, the Roosevelt administration also adopted the New Deal to intervene in the economy.  The Keynesian economics emerging in the 1930s provided the theoretical basis for left-wing government to intervene in the economy.

As the influence of the labour movement started to decline in 1970s and the Keynesain economics met the stagflation problem in practice, the right-wing monetarist school began to dominate economics. The monetarist school advocates that government should withdraw from economy and leave all except law and order to the market. The social, economical and political development since 1980 restarted the wealth concentration process, and the level of wealth concentration at the beginning of the 21^st century approaches that on the eve of world war one. These changes in history demonstrate that the wealth or income inequality cannot be solved by the market mechanism alone. The reduction in the wealth inequality between world war one and 1970s was not achieved by market mechanism. Piketty’s work is a refutation of Kuznets curve, which was proposed in 1953 by American economist Simon Kuznets, a Nobel Prize winner in economics, to describe the relationship between income inequality and the level of economic development. Kuznets curve is an “inverted U” shaped curve, suggesting that the income inequality will grow large initially and then decreases as economy grows.

Many conclusions in economics are drawn from time series data. As I used to work on biomedical research, I know well that biomedical researchers would not accept results from an individual’s time series data. For example, a patient with cold and fever for 5 days may take a sweet and then recover after 2 more days. If we analyze this process with economic time series method, we may conclude that the sweet is the most important factor for the patient’s recovery. Because of this, biomedical researchers only accept results with randomized control groups. Since macroeconomic analysisoften relies on one unit with many time points or many units at one time point, which lacks the control group in the sense that biomedical researchers understand it, Piketty’s view that short-term results are not really reliable and correct results may be obtained by examining the historically long series data is a very precious one.