Nishimura K, Zhang J
J Public Econ. 1992 Jul;48(2):239-58. doi: 10.1016/0047-2727(92)90029-f.
A 1986 "model of public pensions is generalized to allow for endogenous fertility. We show that gifts to the old, which can be viewed as social security contributions, are always positive in the steady state. An optimal stationary allocation is sustainable if savings are zero and fertility is exogenous. However, the optimal allocation is in general not sustainable. In particular, if a government enforces a social security plan setting the pension level at the optimal gifts and individuals optimize under the pension constraint, the resulting sustainable outcome is in general different from either the optimal or Nash outcome." The geographical focus is on developed countries.
1986年的一个“公共养老金模型”被推广以考虑内生生育率。我们表明，对老年人的馈赠（可视为社会保障缴款）在稳态下总是正的。如果储蓄为零且生育率是外生的，最优静态配置是可持续的。然而，最优配置通常是不可持续的。特别是，如果政府实施一项社会保障计划，将养老金水平设定为最优馈赠水平，且个人在养老金约束下进行优化，那么由此产生的可持续结果通常不同于最优结果或纳什均衡结果。”地理重点是发达国家。
