People who buy their own health insurance are being asked to pay 20 percent more for the same coverage, according to the Kaiser Family Foundation, but the study provided little data on what's behind spiking premiums. In a study released today, the foundation found that about three-fourths of the country's 14 million people who don't get group coverage said they faced premium increases. Most paid the increase, perhaps trapped by the inability to find other coverage because of preexisting conditions, researchers said.