The Effect of Disability Insurance Payments on Beneficiaries' Earnings
利用美国社保残疾保险（DI）的福利公式不连续变化，采用回归扭结设计估计了保险金对受益人收入和就业的收入效应，发现每增加1美元保险金使收入减少0.20美元，每千美元使就业率下降1.3个百分点。
A crucial issue is whether social insurance affects work decisions through income or substitution effects. We examine this in the context of US Social Security Disability Insurance (DI), exploiting discon tinuous changes in the benefit formula with a regression kink design to estimate the income effect of payments on earnings and employment. Using administrative data on all new DI beneficiaries from 2001 to 2007, our preferred estimate is that an increase in DI payments of $1 causes an average decrease in beneficiaries' earnings of $0.20 and that annual employment rates decrease by 1.3 percentage points per $1,000 of DI payments. These findings suggest that the income effect accounts for a majority of DI-induced reductions in earnings.