productivity: a new technology is "more risky" and more productive on average. In this context, the adoption of the new technology from a low level of income (close to subsistence) generates a gradual increase in the investment to output ratio.

College-educated workers entering the labor market in 1940 experienced a 4-fold increase in their labor earnings between the ages of 25 and 55; in contrast, the increase was 2.6-fold for those entering the market in 1980. For workers without a college education these figures are 3.6-fold and...

The authors present a simple, two-period model of human capital accumulation on the job and through college attainment. They use a calibrated version of the model to explain the observed flattening of the life-cycle earnings profiles of two cohorts of workers. The model accounts for more than 55...