The number of U.S. residents who have health insurance but not the ability to afford adequate medical care continues to climb. About 25 million Americans did not have sufficient coverage last year to shield them from financial hardship if they ended up in the emergency room or were seriously ill, according to a study by the Commonwealth Fund. The continuous rise in medical costs, combined with a growing number of insurance plans that require patients to pay a higher portion of their medical bills, has led to a 60% increase in the number of underinsured adults from 2003 to 2007, according to the study.