Natural Selection in Markets

对于企业利润最大化这一假设，最常见的理论辩护是，否则它们将被赶出市场。其理念是，无论出于何种原因，只有那些成功实现利润最大化的公司才能够吸引或积累足够的资本来生存和发展。尽管这种直觉已经存在了很长时间(参见Alchian (1950), Friedman（1953）和Winter(1964, 1971))，但还没有在一般均衡环境下进行研究。这种观点也有批评者。特别是，Koopmans（1957）认为，引用外部动态过程来支持关键行为假设的有效性并不是一种令人满意的继续方式。在提出这一建议的工作中，我们在一个简单的一般均衡模型中检验了这一假设，在这个模型中，企业从留存收益中为当前运营提供资金，而不需要进入外部金融资本市场。这种动态，就像温特所讨论的那样，推动着企业运营的规模。我们发现，在所有获得相同技术的公司中，只有那些最接近利润最大化的公司才能生存下来。但库普曼斯是对的。选择利润最大化者的倾向并不会产生相应的生产者总效率选择。在缺乏金融资本市场的情况下，留存收益动态无法在企业之间重新分配资金，从而实现生产者效率的结果。资本市场的加入“解决”了这个问题，因为如果所有投资者都有理性预期，而且市场是动态完备的，那么均衡是有效的。但这回避了一个问题。更有趣的是，如果不是所有投资者都有理性预期，会发生什么。在这种情况下，结果可能比没有金融资本市场还要糟糕。我们的研究计划可以被描述为认真对待Koopmans的担忧。我们感兴趣的是，当企业不一定能实现利润最大化，投资者不一定是理性的，但经济自然选择的力量在起作用时，会发生什么。均衡序列显示了什么特征？它的渐近性质是什么？平衡点序列或极限平衡点是否存在最优性？我们知道利润最大化者在某些情况下会被选择，而在其他情况下则不会，但是适合决策规则是否可以被普遍表征？当利润是随机的，公司不能通过套利来估值时，这些问题就特别有趣了。在这种情况下，不清楚公司的目标是什么。我们的初步调查表明，即使资本家想要预期利润最大化，也没有选择这一目标的倾向。相反，我们推测，将会有企业选择，以最大化其留存收益的预期增长率。这与预期的利润最大化不一致，但与流行的关于大公司目标的评论是一致的。

The most common theoretical defense of the hypothesis that firms maximize profits is that otherwise they will be driven out of the market. The idea is that only those firms which for whatever reason succeed in maximizing profits will able to attract or accumulate enough capital to survive and grow. Although this intuition has been around for a long time (see Alchian (1950), Friedman (1953) and Winter (1964, 1971)) it has not been investigated in a general equilibrium setting. The argument also has its critics. In particular, Koopmans (1957) argued that referencing an external dynamic process to support the validity of a key behavioral assumption is not really a satisfactory way to proceed. In the work leading up to this proposal we have examined this hypothesis in a simple general equilibrium model in which firms fund current operations from retained earnings, without access to external financial capital markets. This dynamic, much like that discussed by Winter, drives the scale of firm operation. We found that among all firms having access to the same technology only those that come closest to maximizing profits survive. But Koopmans is nonetheless right. The tendency to select for profit maximizers does not generate a corresponding selection for aggregate producer efficiency. In the absence of markets for financial capital, the retained earnings dynamic is not able to reallocate funds across firms so as to achieve producer efficient outcomes. The addition of capital markets `solves` the problem in that if all investors have rational expectations, and markets are dynamically complete, then the equilibrium is efficient. But this begs the question. More interesting is what happens if not all investors have rational expectations. In this case the result can be even worse than without financial capital markets. Our research plan can be characterized as taking Koopmans' concern seriously. We are interested in what does happen when firms do not necessarily maximize profits, and investors are not necessarily rational, but the forces of economic natural selection are at work. What characteristics does the sequence of equilibria display? What are the asymptotic properties? Are there any optimality properties for either the sequence of equilibria or for the limit equilibria? We know that profit maximizers are selected for in some settings and not in others, but can the fit decision rules be characterized generally? These questions are particularly interesting when profits are random and firms cannot be valued through arbitrage. In this case it is not clear what objective to attribute to a firm. Our preliminary investigation suggest that there is no tendency to select for expected profit maximization even when that is what capitalists want. Instead we conjecture that there will be selection for firms that act so as to maximize the expected growth rate of their retained earnings. This is not consistent with expected profit maximization, but it is consistent with popular commentary about the objectives of large corporations.