"Nearly one in four people with Medicare have private Medicare supplemental insurance plans, known as "Medigap" plans that help with health care expenses not otherwise covered by Medicare. This analysis provides a detailed look at the Medigap market, including national and state trends in enrollment and premiums for the various Medigap plans. Though Medigap policies by law must offer a set of standardized benefits, the analysis finds that monthly premiums for identical plans vary greatly both across the country and within states. Also, more than half of all Medigap enrollees in 2010 were in plans that cover Medicare's entire Part A and B deductibles, according to this analysis. These enrollees could potentially be affected by policy changes to discourage or prohibit "first dollar" Medigap coverage, as proposed in some of the recent debt-reduction recommendations. The report is authored by researchers at the Kaiser Family Foundation and the University of California at Los Angeles."