Characterizing Efficient Social Insurance Institutions: Theory and Computation

这项研究将发展理论和计算方法来表征有效的社会保险机构。我们将社会保险机构定义为一个强制性的政府运营计划，它提供一系列国家或有税收（保费或缴款）和转移支付（福利），涵盖一系列明确定义的风险。一个有效的社会保险机构是指以最低的成本向系统中的个人提供一定水平的福利的机构。我们的研究将试图提供有效的社会保险机构的特征，包括以下风险：1）长寿，通过强制性养老金或“老年保险”，2）残疾，通过残疾保险，3）失业，通过失业保险，和4）医疗保健费用，通过医疗保险。 社会保险的另一个目标是收入和/或财富的终身再分配。这可以被看作是第五类风险的保险，即为那些具有某些固定特征或“类型”的个人提供的保险，这些特征或“类型”可能会导致终身就业、收入、财富和福利的永久性降低。社会保险计划在发达经济体中规模庞大且普遍存在。在美国，2000年，社会保障（老年、残疾和失业保险）、医疗保险、医疗补助的支出占联邦总支出的48.3%，占国内生产总值的9.8%（美国国会预算办公室）。所有预测都表明，除非福利减少，否则随着婴儿潮一代的老龄化和开始退休，社会保险支出将在未来几十年迅速增长。虽然有人提议通过各种“私有化”计划将社会保险费用从政府转移到私营部门，但各种道德风险和逆向选择问题阻碍了私营保险市场的运作。我们把市场的不完全性作为政府强制提供保险的主要理由，并作为我们分析的基本出发点。我们假设政府可以强制全民参与，但我们也假设它面临着与私人保险机构（如果它们存在的话）相同的信息约束。我们通过两种非常不同但相关的策略来处理这些基本的信息不对称：1）“动态机制设计”（DMD）方法，其中我们在满足某些参与和激励约束的所有可能策略的无限维空间上搜索有效策略，2）“参数机制设计”（PMD）方法，即我们在有限时间内寻找“近似有效”的社会保险制度，利用这些技术，我们不仅可以刻画有效社会保险制度的形式，还可以量化当前社会保险制度的低效率程度。我们希望能够将最佳的社会保障和残疾保险计划作为美国和其他发达经济体社会保险全面综合分析的一部分。鉴于社会保险占GDP的很大比例，发现更有效的社会保险计划可能节省成本，这为这项研究提供了强有力的实际依据。

This research will develop theoretical and computational approaches for characterizing efficient social insurance institutions. We define a social insurance institution as a compulsory government-run program that provides a set of state-contingent taxes (premiums or contributions) and transfers (benefits) that cover a well-defined set of risks. An efficient social insurance institution is one that provides a given level welfare to the individuals in the system at minimal cost. Our research will attempt to provide characterizations of efficient social insurance institutions that cover the following risks: 1) longevity, via mandatory pensions or "old age insurance", 2) disability, via disability insurance, 3) unemployment, via unemployment insurance, and 4) health care costs, via medical insurance. Another objective of social insurance is lifetime redistribution of income and/or wealth. This can be viewed as insurance for a fifth class of risks, namely insurance for individuals who have certain fixed characteristics or "types" that may lead to permanently lower lifetime employment, earnings, wealth, and welfare.Social insurance programs are large and pervasive in developed economies. In the U.S., spending on Social Security (Old Age, Disability, and Unemployment Insurance), Medicare, Medicaid amounted to 48.3\% of total Federal spending and 9.8\% of GDP in 2000 (U.S. Congressional Budget Office). All forecasts indicate that unless benefits are reduced, social insurance spending will grow rapidly over the coming decades as the baby boomers age and start to retire. Although there have been proposals to shift the costs of social insurance from the government to the private sector via various "privatization" schemes, a variety of moral hazard and adverse selection problems hinder the operation of private insurance markets. We take market incompleteness as the principal rationale for mandatory government provision of insurance, and as the basic point of departure for our analysis. We assume that the government can compel universal participation, but we also assume that it faces the same informational constraints as private insurance institutions would face if they existed. We deal with these fundamental informational asymmetries via two very different but related strategies: 1) a "dynamic mechanism design" (DMD) approach where we search for an efficient policy over an infinite-dimensional space of all possible policies that satisfy certain participation and incentive constraints, and 2) a "parametric mechanism design" (PMD) approach where we search for an "approximately efficient" social insurance institution in a finite-dimensional subspace of social insurance institutions and where incentive constraints are ignored.Using these techniques we will not only be able to characterize the form of efficient social insurance institutions, we will also be able to quantify the degree of inefficiency in current social insurance institutions. We expect to be able to characterize optimal social security and disability insurance programs as part of a comprehensive, integrated analysis of social insurance in the U.S. and other developed economies. Given the large share of GDP devoted to social insurance, the potential cost savings from discovering more efficient social insurance programs provides a strong, practical rationale for this research.