This paper by Fatih Guvenen and Greg Kaplan is worth a read by anyone interested in inequality trends. An important excerpt:
Since 2000, different measures of top income inequality have exhibited very different trends. Top income shares based on measures of total income show a continued rise, whereas top income shares based on wage and salary income show no increase in inequality post-2000. The most important difference between these two measures of income is the income that accrues to S-corporations....
But interpreting trends in the S-corporation component is extremely difficult. Feenberg and Poterba (1993), Gordon and Slemrod (2002), and Cooper et al. (2016) warn that much of the recent increase in S-corporation income is income that previously accrued to C-corporations. Such income is not “new” income earned by top earners but is simply income that was previously labeled as corporate income rather than household income.