This map shows median home values plotted against median household income in an effort to illustrate where the least affordable housing in the U.S. is located. The Bay Area, not surprisingly, has some of the least affordable housing in the country – both in absolute terms, and in terms relative to income. In San Francisco proper, the median home value is $800,000 with a median income of $81,000, giving a price-to-income ratio of nearly 10 to 1. In Marin County, the median home value is $815,000 with a median income of $93,000. This ratio is 8.8 times the median income of the county. In Silicon Valley, housing is still pricey, but many people are able to make up for it with higher incomes: San Mateo County has a ratio of 8.3, and Santa Clara County has a ratio of 7.3.