Adult children are moving back home after college often because rents are rising faster than fixed incomes can bear. Is that having an effect on the average size of a Bay Area family household?

Here’s the average size of a family living together in the Bay Area by county, according to the latest update of census data.1. Santa Clara — 3.43 people2. San Mateo — 3.393. Alameda — 3.363. Solano — 3.365. Contra Costa — 3.346. Napa — 3.297. San Francisco — 3.148. Marin — 3.029. Sonoma — 2.59Other than Sonoma County, all of these numbers are well above the national rate of 2.64 family members per household. The numbers have also risen over time; in 2010, Santa Clara was at 2.86 and San Mateo at 2.72.

Source: U.S. Census Bureau ACS table S1101

Daniel J. Willis