Why Is Income Inequality Increasing?

According to a new Brookings study by Claudia Goldin and Lawrence Katz, much of the increase in income inequality is due to an increase in the education premium:

Another key point we will make is that the majority of the increase in wage inequality since the 1980 has come from rising education wage differentials, particularly rising returns to post-secondary schooling.

This disputes earlier research blaming skill-based technological change, or more surplus going to capital, or whatever. It also disputes Paul Krugman's assertion that it is all George W. Bush's fault. It's a perfect example of how convoluted economics can be, especially when you are looking for policy implications.