Californians living in the Bay Area are more likely to lack health insurance than people in other parts of the state. The U.S. Census Bureau reports that in 2007, 6.5 million Californians lacked health insurance coverage.

Some point to unemployment for the large number of people lacking health insurance. UCLA Center for Health Policy Research director Shana Alex Lavarreda told the San Francisco Chronicle that smaller counties tend to offer more seasonal employment options.

"In rural, smaller counties, you just don't have large, stable job-based coverage pools like you do in the large counties with much larger employers," she told the paper.

Other research has pointed to a variety of factors such as income and education level that also affect the likelihood of someone having health insurance.

Under health care reform, all citizens will be required to obtain health insurance, which should greatly decrease the number of people lacking coverage. In Massachusetts, where health insurance is required, only 7.8 percent of people under the age of 65 didn't have insurance in 2007, according to the U.S. Census Bureau.