The Estimation of Wage Gains and Welfare Gains in Self-Selection Models
考虑教育、培训、工会等活动对工资影响的自选择模型，指出过去模型忽略了回报率的个体差异作为选择偏差的来源，并检验了这种异质性的存在及其对工资和福利收益的影响。
In this paper we consider the basic self-selection model for the effects of education, training, unions, and other activities on wages. We show that past models have ignored 'heterogeneity of rewards' to the activity--i.e., differences across individuals in the rate of return to the activity--as a source of selection bias. We model such heterogeneity, show how its presence can be tested, and draw out its implications for the wage and welfare gains to the activity. An empirical application provides strong support for such heterogeneity.