Joblessness and the accompanying loss of health benefits drove an additional 3.7 million people into the Medicaid program last year, the largest single-year increase since the early days of the government insurance plan, according to an annual survey by the Kaiser Family Foundation.

Enrollment in the program, which provides comprehensive coverage to the low-income uninsured, grew by 8.2 percent from December 2008 to December 2009, the second-largest rate of increase in the 10 years that Kaiser has conducted the survey. There were 48.5 million people on Medicaid at the end of 2009, or about one of every six Americans.

Every state showed enrollment growth, with nine above 15 percent and Nevada and Wisconsin above 20 percent.

Those kinds of increases exact a heavy toll on state budgets, as states share the cost of the Medicaid program with the federal government. The foundation, an independent nonprofit group that conducts research on health policy, found that spending on Medicaid grew 8.8 percent in 2009, the largest increase since 2002.