In fact, the number of children under 18 in Bay Area households is generally lower than the national average, according to the latest update to census data.1. Contra Costa — 23.5%2. Santa Clara — 23.1%3. Solano — 23%4. Napa — 21.9%5. San Mateo — 21.5%6. Alameda — 21.4%7. Sonoma — 20.6%8. Marin — 20.5%9. San Francisco — 13.5%[bar color=”Accent-Color” title=”1. Contra Costa — 23.5%” percent=”23.5″][bar color=”Extra-Color-1″ title=”2. Santa Clara — 23.1%” percent=”23.1″][bar color=”Accent-Color” title=”3. Solano — 23%” percent=”23″][bar color=”Extra-Color-1″ title=”4. Napa — 21.9%” percent=”21.9″][bar color=”Accent-Color” title=”5. San Mateo — 21.5%” percent=”21.5″][bar color=”Extra-Color-1″ title=”6. Alameda — 21.4%” percent=”21.4″][bar color=”Accent-Color” title=”7. Sonoma — 20.6%” percent=”20.6″][bar color=”Extra-Color-1″ title=”8. Marin — 20.5%” percent=”20.5″][bar color=”Accent-Color” title=”9. San Francisco — 13.5%” percent=”13.5″]Contra Costa County shows the most kids, at 23.5 percent of the population, which is just about par with the national average of 23.1 percent. On the lower end is Marin County, with 20.1 percent, and San Francisco has the lowest number, with 13.5 percent.
Numbers derived from: U.S. Census Bureau ACS table S0101
Given the high cost of living in the Bay Area, some people opt not to raise a family here.