<p>The academics have the answer–from the COHE</p>
<p>"In The Race Between Education and Technology (Belknap/Harvard University Press), Goldin and Katz emphasize that plenty of skills-biased technological change occurred long before anyone had heard of Bill Gates. The mass introduction of electric power in the 1910s, for example, increased the complexity of many jobs and increased employers’ demand for skill.</p>
<p>But that rising demand, in Goldin and Katz’s account, was outpaced during most of the 20th century by a soaring supply of educated workers. Between 1915 and 1950, the national high-school-graduation rate rose from roughly 15 percent to roughly 60 percent, and college attend-ance also spiked. As their numbers ballooned, educated workers could no longer command so much more in wages. Between 1915 and 1950, the college wage premium (the amount by which college graduates outearn people who hold only a high-school diploma) and the high-school wage premium (the amount by which high-school graduates outearn high-school dropouts) both fell sharply. The postwar period famously saw a broad prosperity, with wages growing for people of all educational levels.</p>
<p>Then, around 1970, something changed. High-school graduation rates flattened near 70 percent, where they remain. College attendance continued to grow, but the college-completion rate — that is, the percentage of a population cohort that earns a bachelor’s degree — stagnated for more than a decade. (In the 1990s, women’s college-completion rate began to grow strongly again, but the rate for men is still roughly what it was 40 years ago.)</p>
<p>“There was enormous growth in educational attainment between 1900 and 1970,” Goldin says in an interview. “But after 1970, the growth in attainment became much more sluggish. Putting those two parts together, you can explain a large amount of the story of wage inequality in the 20th century.”</p>