Not so much change, and if you look you will see there is also not so much
change for non-family households. The Census pdf is here.
I have covered this ground before, but the myth of "changing household size
means economic progress has been just fine" dies hard.
Unfortunately, Tyler continues his recent habit of truncating the data to make his case look as strong as possible. (He also strangely reports data for family households rather than all households, but that doesn't sway the results). What if he'd shown all U.S. households for the whole history of the Current Population Survey?
Persons Per Household
Now we get a nuanced story. Changing household size was a huge deal between 1970 and 1990, and no deal at all between 1990 and 2010. Since stagnationists like Tyler usually start their tale of woe in 1973, critics can and should complain that household income is a biased measure of individual income. Adjusted for family size, income rose about 20% more between 1970 and 1990 than stagnationists like to claim.
At the same time, of course, stagnationists are right to assert that changing household size has been irrelevant since 1990. But making this concession ruins their narrative. Changing family size was a big deal in the 70s and 80s. Growth was pretty good in the 90s. So instead of four decades of woe, the stagnationists are down to one. If they were upfront about this - if they framed stagnation as a current event rather than Big Think economic history - I'd take them more seriously.
Update: Tyler acknowledged some role for declining family size before 1989 in both The Great Stagnation and this post. But I stand by my complaints about the post I'm discussing here.