By the way, here’s a paragraph from the original draft of my and Mark’s WSJ essay that was deleted because of space constraints:
Consider that in 1975 81 percent of U.S. households earned less than $75,000 in annual income (in constant 2009 dollars); today (or 2009, the latest year for which data are available) that share is only 68 percent. Put differently, nearly one-third of all households in America today have annual incomes of $75,000 or more, while in 1975 only one-fifth of U.S. households were so well off. Drilling further down into the data reveals that for each of the Census Bureau’s five income categories below $75,000, the percentages of American households earning these relatively modest incomes have fallen, while for each of the two higher-income categories – $75,000 to $99,999, and $100,000 or more – the percentages of U.S. households earning incomes in each of these categories have risen.
And in this paragraph Mark and I didn’t mention the further point that the average number of occupants of American households fell by more than 10 percent between the mid-1970s and today.