Earnings within Education Groups and Overall Productivity Growth
构建了一个包含内生人力资本投资、天赋分布和技术进步的理论模型，解释为何各教育组平均收入增长慢于整体平均工资，且高教育组相对收入上升，但整体收入不平等未必扩大。
To offer a possible interpretation for recent empirical findings on earnings growth, this paper constructs a simple model with endogenous human capital investment, a distribution of natural abilities, and unbiased technological progress. The model predicts that in the long run, average earnings within any education group will grow more slowly than average wages overall. It also predicts that average earnings in high-education groups ultimately will rise relative to average earnings in low-education groups. In the model, these processes do not imply secular increases in the degree of inequality in the overall cross-sectional distribution of earnings.