AI 中文总结
该论文针对存在异质性风险且无不可保险系统性风险的市场，证明多期相互保险的遍历定理，提出仅用短期合约即可实现极限效用的机制，可应用于风险分摊经济体及保险产品设计。
AI 中文摘要
假设市场中有N个异质性代理人，他们面临异质性风险，但不存在不可保险的系统性风险因素。这些代理人可相互达成任意金融合约，条件是合约在处于共同状态的代理人联盟下是自我执行的。我们证明，在温和条件下，当N趋向无穷时，这唯一确定了每个代理人的极限效用。该结果是一个遍历定理：随着人口增长，问题的自由度会崩溃，使得相同状态的代理人在极限中被同等对待。我们展示了一种仅使用短期合约即可实现该极限的明确、切实可行的机制。该模型既适用于异质性代理人通过自我执行合约分摊异质性风险的经济体，也适用于养老金等最优保险产品的设计。
英文摘要
Suppose there are $N$ heterogeneous agents in a market with idiosyncratic risks but no uninsurable systematic risk factors. These agents may agree arbitrary financial contracts with one another, subject to the condition that contracts are self-enforcing under coalitions of agents in a common state. We show that, under mild conditions, this uniquely determines the limiting utility of every agent as $N$ tends to infinity. The result is an ergodic theorem: as the population grows, the number of degrees of freedom in the problem collapses, so that agents in the same state are treated identically in the limit. We exhibit an explicit, practically realisable mechanism achieving this limit using only short-dated contracts. The model can be applied either to an economy of heterogeneous agents pooling idiosyncratic risk through self-enforcing contracts or to the design of optimal insurance products such as pensions.
