Following up on that last post, depending on how you calculate it, the convergence between median family income and per capita GDP since 1984 occurs either completely or predominantly during the median income drops that surround recognized recessions.
Arithmetically, the difference between median family and per capita income dropped by $14,500 between 1984 and 2012. $14,500 of that change was associated with recessions.
Geometrically, per capita GDP increased 61% from '84 to '12. Median income increased by 8.1%. Between median income recessions, per capita income outpaced median income 43% to 30%, significant but not startling. During median income recessions, per capita income increased 12%. Median income dropped 17%.
By the way, I realize that per capita GDP and median household income measure slightly different things. Average household size, for example, decreased by about 7% over this time period, which would explain some of the difference in non-recession growth. There are, no doubt, other corrections to the baseline trends that explain some differences in growth rates without corresponding increases in inequality.
It seems unlikely, however, that those trends are related to economic cycles. It's hard to believe that average family sizes dropped 8% from 2007 to 2012, or that benefits increased about 15% from 1999-2004 to compensate for the drop in median income. And to the extent that those trends explain the baseline, non-recession convergence of the curves, it only further emphasizes the role of recessions in increasing inequality.
It hasn't always been this way. Prior to 1980, per capita GDP and median household income tracked one another very closely.