Cunha, Flavio, Fatih Karahan, and Ilton Soares (2011), "Returns to Skills and the College Premium." Journal of Money, Credit, and Banking, 43, 39-86.

A substantial literature documents the evolution of the college premium in the U.S. labor market over the last 40 years or so. There are at least three different interpretations of this fact: (i) shifts in the relative supply of and demand for college versus high school labor, (ii) shifts in the relative supply of and demand for skills in the college versus high school sector, and (iii) composition effects. We investigate how each of these components contributes to the dynamics of the college premium and find that all three play a role, but the increase in the college premium is primarily driven by the first component. We also find that during the 1980s, the college premium for high school workers diverged from the college premium for college workers and a substantial fraction of the gap that opens up is primarily due to the increase in the returns to cognitive skills.