Optimal Notional Defined Contributions
研究了用名义固定缴费制替代美国现行社保体系的改革，发现保留现有缴费规则会降低福利，而将缴费集中在职业生涯后期可提高福利，尤其有利于低生产率工人。
Abstract Notional Defined Contributions (NDC) systems mimic the incentive structure of fully funded social security while preserving the pay‐as‐you‐go nature of most current systems. We study size‐preserving social reforms that replace the current U.S. system with NDCs characterized by alternative contribution rules and deficit/GDP ratios. If one retains the current mandatory age‐independent contribution rules, we find a change to an NDC to reduce welfare: the sacrifices in distributive and insurance properties are not compensated by the efficiency gains. NDCs are, however, flexible enough to allow for alternative contribution rules that increase welfare while preserving actuarial fairness. Contributions ought to be age‐dependent and concentrated later in a worker's career. The incentive structure induces an increase in capital accumulation that results, through general equilibrium effects, in welfare gains larger for low‐productivity workers, despite the increase in income inequality as captured by the Gini coefficient.