Regarding Russ’s challenge to Tyler , Ron Muhlenkamp e-mailed to me these data showing that the average size of American households has been shrinking steadily since 1950 . Mr. Muhlenkamp offers this plausible hypothesis (also from his e-mail):
The reason median household income has not grown is because we have far more households per capita than we used to.
One reason is because we have fewer children per household but we also have far more households with little or no earned income (retirees)
Where I grew up Midwest, a generation ago, it was normal for a senior to live with his/her children when they could no longer work to support themselves, (as did My grandparents). Today it is normal for such seniors to live in a separate household
I just sent you a table showing the growth per decade in population and in households.
Median income per capita has increased relentlessly (see also the chapter on consumer spending in my book) median income per HH has not only because (we can afford) more households.