This report from the Kaiser Family Foundations covers key information about the uninsured population in the United States.

From the report:

The number of nonelderly uninsured Americans rose to 50.0 million in 2009—an increase of 4.3 million people—amidst rising unemployment rates and an economic recession.* Nearly all of the elderly are insured by Medicare, yet nearly 700,000 of the elderly were uninsured last year. Because the majority of the nonelderly still receive their health insurance as a job benefit, the steady decline in employer-sponsored health coverage since 2000 and the current weak job market largely explain the growing numbers of uninsured. The safety net of Medicaid and the Children’s Health Insurance Program (CHIP) has prevented a larger increase in the uninsured and, in particular, buffered children from the full effects of the recession.Almost one in five (19%) of the nonelderly was uninsured in 2009 (Figure 1).

Full Report: The Uninsured: A Primer (PDF | 2.67 MB)

Kaiser Family Foundation. (2010). The uninsured: a primer.