The source of the gender differences in labor market outcomes has long been in dispute. The debate has been principally between free market economists, who believe that human capital and women’s family choices are the source of the differences, and institutional economists, who believe that discrimination and institutional barriers in labor markets prevent women from succeeding to the same extent as men.

Recent economic research has linked severe inequality with a weaker middle class, and a weaker middle class with slower economic growth. While academic research has increasingly focused on the economic consequences of inequality, including the economic consequences of a strong or weak middle class, these studies do not, on their own, explain the transmission mechanisms through which inequality affects the economy.

Traditionally perceived as a highly mobile society, the U.S. has recently been shown to be less mobile than many people believe and much less mobile than many other high-income countries, particularly in Europe. This finding has sparked something of a holy war among adherents of competing measures of economic mobility. Those on the political left tend to favor measures of relative mobility. These measures indicate how freely individuals (or their offspring) can change positions in a population distribution ordered along some social dimension, such as income or education.