The optimal earnings test and retirement behavior

This paper quantitatively derives the welfare-improving earnings test within an optimal income tax framework. I construct a life cycle model of labor supply and savings to compute social welfare. The preference parameters are estimated by the method of simulated moments using Japanese data. I find that social welfare under the current earnings test with large changes of marginal tax rates at thresholds is substantially lower than social welfare under the earnings test with a linear tax rate. In addition, an earnings test with negative marginal tax rates will increase social welfare more than a system without negative marginal tax rates.