The relatively small share of PDP enrollees who switched plans at some point between 2006 and 2010 were more likely than those who did not switch to end up in a plan that lowered their premiums. Nearly half (46 percent) of enrollees who switched plans saw their premiums fall by at least 5 percent the following year, compared to 8 percent of those who did not switch plans. But those who switched plans were only slightly more likely than those who did not switch to face lower out-of-pocket costs for drugs during the year