Households or people

In last Sunday's New York Times, Paul Campos (a professor at the University of Colorado law school) says that "the gap between black and white Americans at every income level, remains every bit as extreme as it was five decades ago."  He shows figures of the income ratio of households at the 20th, 40th, 60th, 80th, and 95th percentiles of the black and white income distribution, and they are indeed all virtually unchanged.

Here is a figure he didn't show:  the ratio of per-capita income for blacks relative to per-capita income for whites.

There is a clear and pretty steady increase in the ratio of average black to white income--that is, the gap has declined.  Why the difference?  Campos was comparing households, which may (and usually do) include more than one person.  Average household size has been declining in the United States over the last fifty years--the biggest reasons are later marriage and longer lifespans.  The most plausible way to reconcile the two trends is that average household size has declined more for blacks than for whites.

What is the best way to measure the "gap between black and white Americans?"  You could argue that per-capita income is not the ideal measure--maybe it should be adjusted for age--but it certainly would involve people rather than households.

Campos's general point is that the slow growth of incomes for working-class and middle-class whites in the last couple of decades isn't because blacks have been doing well.  This is true--the only group that has had rapid income growth recently is people with high incomes.  But the gap in black and white incomes has declined, although the decline has been slow.


PS:  The Census data black and white income is at
https://www.census.gov/data/tables/time-series/demo/income-poverty/historical-income-households.html
and
https://www.census.gov/data/tables/time-series/demo/income-poverty/historical-income-people.html