The purpose of doing this is to establish why income distribution follows the pattern it does. If it transpires that our rich, multivariate Mincerian equation, combined with information about statistical distribution, explains little having to do with changes in income distribution, then I would humbly submit that there is a lot of rent-capture going on. John C Halasz suggests that the growth in inequality is spurred by the growth in limited partnerships (mainly in financial services, insurance, and real estate—the FIRE sector); this feeds back into the growth of non-wage income as a share of gross national income. It also leads to a far broader swathe of managers being compensated with options instead of direct salaries, which has been found to lead to certain moral hazard and agency problems (HC). The topic of Eckstein's & Nagypál's paper, however, is earnings inequality (although I spent a considerable amount of time researching income inequality).

One additional omission: I neglected to give adequate attention to the fact that the returns to education were increasing even as the amount of schooling in the workforce was increasing. In other words, a much larger share of the US workforce now has some college, or an advanced degree, than was the case in the 1960s':

The significance of this to an economist is, of course, that while the supply of educated workers grew sharply, it was still overtaken by the increase in demand—reflected by the soaring returns to education.

Here are some of their findings:

• The last quarter of the twentieth century was a period of continuously growing earnings inequality and that this period coincided with an increase in the share of employee benefits in compensation. Furthermore,..., given what we know about the incidence of non-wage compensation, the trend in inequality that we observe in the CPS earnings is probably a lower bound for the trend in compensation inequality.
• In the 41-year period 1961-2002, male wages increased by 75 percent while female wages ... increased by 107 percent. Most of the differential wage growth took place between 1978 and 1994 when...mean wages of men grew a mere 4 percent while those of women increased by 27 percent. In 2002 women earned only 69 percent as much as men, $36,831 compared to $53,661 using annualized 2002 values.)
• Male earnings inequality, measured by the mean-to-median ratio, has been increasing from 1974 to 2002, and female earnings inequality has been increasing from 1981 to 2002. The fact that female wages started to converge to male wages at the same time that inequality within gender groups increased implies that there could be a link between these two phenomena.

• Some differences across the evolution of earnings by ethnic groups. There... has been a decline in the relative wages of Hispanic men, whose wages increased at a rate 20 percent below those of their white counterparts between 1980 and 2002, which led to an increase of the Hispanic/white wage gap from 26 percent in 1970 to 41 percent in 2002. During the same period, the black/white wage gap among men declined slightly from 37 percent to 33 percent, while the gap between other ethnic groups and whites declined from 15 percent to 6 percent. For women, the ethnic wage gaps have been generally smaller

Eckstein & Nagypál are skeptical of the skill-biased technical change argument, although they present evidence for it:

...The ratio of the earnings of college educated workers (college graduate and postgraduate) to those of non–college graduate workers (defined as including groups HSD, HSG and SC) increased substantially. This observation is central to the argument that SBTC is the main cause for the observed rise in inequality.
[p.17b]

There are two notable differences between men and women. First, the greater increase in overall earnings of women shows up clearly for most education groups... Second, the increase in inequality across education groups after 1981 is not as marked for women as it is for men. This is due to the fact that lower-educated women did better in terms of catching up to their male counterparts then did higher-educated women over this period. In fact, college graduate and postgraduate women saw their relative wages compared to men decrease between 1963 and the late ’70s.
[p.17b]