Loukas Karabarbounis and Brent Neiman have a paper on the decline in labor’s share of income.
We start by documenting the pervasive decline in labor shares around the world at the country, U.S. state, and industry levels. Next, we document a decline in the relative price of investment goods, which we later show to be the key factor explaining the global trend in the labor share.
Recall that Timothy Taylor blogged on this topic (although not on this paper in particular). The story is that computers and computer-driven machines are getting cheaper, leading businesses to substitute capital for labor, causing labor’s share of income to fall.
To me, this, along with factor price equalization, is the most intuitively plausible account for trends in the distribution of income over the past twenty years.