Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139;
School of Law, Northwestern University, Chicago, IL 60611-3069;
Proc Natl Acad Sci U S A. 2014 Dec 16;111(50):17777-82. doi: 10.1073/pnas.1406755111. Epub 2014 Dec 1.
Risk aversion is one of the most basic assumptions of economic behavior, but few studies have addressed the question of where risk preferences come from and why they differ from one individual to the next. Here, we propose an evolutionary explanation for the origin of risk aversion. In the context of a simple binary-choice model, we show that risk aversion emerges by natural selection if reproductive risk is systematic (i.e., correlated across individuals in a given generation). In contrast, risk neutrality emerges if reproductive risk is idiosyncratic (i.e., uncorrelated across each given generation). More generally, our framework implies that the degree of risk aversion is determined by the stochastic nature of reproductive rates, and we show that different statistical properties lead to different utility functions. The simplicity and generality of our model suggest that these implications are primitive and cut across species, physiology, and genetic origins.
风险规避是经济行为最基本的假设之一，但很少有研究探讨风险偏好从何而来，以及为什么人与人之间存在差异。在这里，我们提出了一个关于风险规避起源的进化解释。在一个简单的二元选择模型的背景下，如果生殖风险是系统性的（即在给定的一代中个体之间相关），那么自然选择就会产生风险规避。相比之下，如果生殖风险是特质性的（即在给定的每一代中个体之间不相关），那么就会产生风险中性。更一般地说，我们的框架意味着风险规避的程度取决于生殖率的随机性质，我们还表明，不同的统计特性会导致不同的效用函数。我们模型的简单性和通用性表明，这些含义是原始的，并且跨越了物种、生理学和遗传起源。
