NBER Publications by Shinichi Nishiyama

While privatizing Social Security can improve labor supply incentives, it can also reduce risk sharing when households face uninsurable risks. We simulate a stylized 50-percent privatization using an overlapping-generations model where heterogenous agents with elastic labor supply face idiosyncratic earnings shocks and longevity uncertainty. When wage shocks are insurable, privatization produces about $21,900 of new resources for each future household (growth adjusted over time) after all households have been fully compensated for their possible transitional losses. However, when wages are not insurable, privatization reduces efficiency by about $5,600 per future household despite improved labor supply incentives. We check the robustness of these results to different model specications an...

Fundamental tax reform is examined in a heterogeneous overlapping-generations (OLG) model in which agents face idiosyncratic earnings shocks and uncertain life spans. Following Auerbach and Kotlikoff (1987), a Lump-Sum Redistribution Authority is used to rigorously examine efficiency gains over the transition path. A progressive income tax is replaced with a flat consumption tax (for example, a value-added tax or a national retail sales tax). If shocks are insurable (that is, no risk), this reform improves (interim) efficiency, a result consistent with the previous literature. But if, more realistically, shocks are uninsurable, this reform reduces efficiency, even though national wealth and output increase over the entire transition path. This efficiency loss, in large part, stems from red...

Several important empirical studies (e.g., Altonji, Hayashi, and Kotlikoff, 1992, 1996, 1997) find that households are not altruistically-linked in a way consistent with the standard Ricardian model, as put forward by Barro (1974). We build a two-sided altruistic-linkage model in which private transfers are made in the presence of two types of shocks: an 'observable' shock that is public information (e.g., public redistribution) and an 'unobservable' shock that is private information (e.g., idiosyncratic wages). Parents and children observe each other's total income but not each other's effort level. In the second-best optimum, unobservable shocks are only partially shared whereas, for any utility function satisfying a condition derived herein, observable shocks are fully shared. The model...