The Census Bureau recently updated its Characteristics of New Housing data, revealing the current size and shape of the American household and home.
The size of the median new single-family home continues to grow. Homes completed in 2017 were 14 percent bigger than in 2009, whereas the lots of homes continue to shrink. Over that same period, the median square footage of new-home lots went down 20 percent, from 11,000 sf to 8,800 sf. According to Bloomberg, one reason behind the growth of new-home sizes, "has surely been that Americans in the top 20 percent of the income distribution have a lot more money to spend than they did four decades ago, and many have chosen to maximize their utility by spending some of it on guest bedrooms, home offices and extra bathrooms."
The average U.S. household is 24 percent (or 0.82 people) smaller than it was in the early 1960s. This downtrend has flattened out a lot since the Great Baby Boomer Move-Out of the 1970s, and household size has even on occasion gone up for a year or two, sometimes due to recessions keeping young people with their parents, and sometimes due to data revisions, although last year saw a slight uptick perhaps caused by Millennials finally getting married. Still, there are markedly fewer Americans per house or apartment than there were a few decades ago.