中文摘要
本文采用一个包含个体异质性风险和不完全资产市场的生命周期异质性主体模型，刻画美国面向低收入单亲父母的收入支持制度的最优改革。我们以美国税收—转移支付制度为基准政策，并使用从当前人口调查（CPS）中抽取的单亲母亲样本，评估使未来单亲母亲的平均预期效用最大化的改革方案。当政策无法根据子女年龄分类设定（tagging）时，最优改革要求将无工作收入支持提高约15%，并将面向低工资劳动者的劳动收入补贴降低约50%。这一改革带来了可观的福利增益。根据子女年龄分类设定政策，使政府在为有学龄前子女的单亲母亲提供保障与为有学龄子女的单亲母亲提供工作激励之间的权衡更为有利，从而扩大了其在整个生命周期中平滑边际效用的空间。在分类设定政策下，有学龄前子女的母亲获得的无工作收入支持大幅提高，且不再获得劳动收入补贴。分类设定政策带来了额外的福利增益。
Abstract
We characterize the optimal reform of U.S. income support for low-income single parents using a life-cycle heterogeneous agent model with idiosyncratic risk and incomplete asset markets. We use the U.S. tax-transfer system as the benchmark policy and a sample of single mothers drawn from the CPS to assess reforms that maximize average expected utility among single mothers-to-be. When policy cannot be tagged by the age of the children, the optimal reform calls for an increase in out-of-work income support by about 15 percent, and a decrease in earnings subsidies to low-wage workers by roughly 50 percent. This reform delivers substantial welfare gains. Tagging policy by the age of the children makes the government’s trade-off between providing insurance to single mothers with children of pre-school age, on the one hand, and providing work incentives to those with school-age children, on the other hand, more favorable, thus increasing their scope for smoothing marginal utility throughout the life cycle. With tagging, mothers of pre-school age children get a substantial increase in out-of-work income support and no earnings subsidies. Tagging brings additional welfare gains.