Education, Variation in Earnings, and Nonmonetary Compensation
利用NAS-NRC双胞胎后代数据，发现低教育水平者收入可充分代表总补偿，而高教育者则不然；加入职业选择原因变量后，高教育组收入差异解释度提高9%，性别工资差距降低近40%。
The NAS-NRC Twin Offspring data support the proposition that for those with low levels of education, earnings may be an adequate proxy for compensation, whereas the opposite holds for highly educated individuals. The inclusion of variables that control for reasons (monetary or nonmonetary) individuals chose their occupation explains an additional 9 percent of the variation in earnings for those with 16 or more years of education (and lowers the male female wage gap by almost 40 percent) and only an additional 2 percent for those with 15 years or less (no affect on male-female wage gap).