Inequality trends

In this latest New York Times piece Gregory Mankiw discusses income inequality. He asks, What accounts for rising inequality? His answer is "educational slowdown". He writes,

The best diagnosis so far comes from two of my Harvard colleagues, Claudia Goldin and Lawrence F. Katz, in their forthcoming book “The Race Between Education and Technology” (Harvard University Press). [...] Their bottom line: “the sharp rise in inequality was largely due to an educational slowdown.”

According to Professors Goldin and Katz, for the past century technological progress has been a steady force not only increasing average living standards, but also increasing the demand for skilled workers relative to unskilled workers. Skilled workers are needed to apply and manage new technologies, while less skilled workers are more likely to become obsolete.

For much of the 20th century, however, skill-biased technological change was outpaced by advances in educational attainment. In other words, while technological progress increased the demand for skilled workers, our educational system increased the supply of them even faster. As a result, skilled workers did not benefit disproportionately from economic growth.

But recently things have changed. Over the last several decades, technology has kept up its pace, while educational advancement has slowed down. The numbers are striking. The cohort of workers born in 1950 had an average of 4.67 more years of schooling than the cohort born in 1900, representing an increase of 0.93 year in each decade. By contrast, the cohort born in 1975 had only 0.74 more years of schooling than that born in 1950, an increase of only 0.30 year a decade.

Because growth in the supply of skilled workers has slowed, their wages have grown relative to those of the unskilled. This shows up in the estimates of the financial return to education made by Professors Goldin and Katz. In 1980, each year of college raised a person’s wage by 7.6 percent. In 2005, each year of college yielded an additional 12.9 percent. The rate of return from each year of graduate school has risen even more — from 7.3 to 14.2 percent.

The question here is, Given that more and more people are in some form of post-secondary education why has there been "educational slowdown"? Has demand really increased so much that the education system just can't keep up?

(HT: Greg Mankiw)