The number of underinsured U.S. adults—people who have health coverage that does not adequately protect them from high medical expenses—has soared, according to a study from the Commonwealth Fund. In a study is published online in Health Affairs in an article How Many Are Underinsured? Trends Among U.S. Adults, 2003 and 2007. For the study, the researchers analyzed data from the Commonwealth Fund 2007 Biennial Health Insurance Survey, which interviewed adults ages 19 and older from June through October 2007. As of 2007, there were an estimated 25 million underinsured adults in the United States, up 60 percent from 2003. The authors of the report say much of the growth comes from the ranks of the middle class. While low-income people remain vulnerable, middle-income families have been hit hardest. For adults with incomes above 200 percent of the federal poverty level (about $40,000 per year for a family), the underinsured rates nearly tripled since 2003.