4 percent: That’s how many bankruptcy filings by non-elderly adults were the result of medical expenses, reachers from MIT have found. That’s a figure far lower than most estimates, which often put the number around 50 percent or higher. The research, published in the New England Journal of Medicine, used medical and financial information from roughly 930,000 people. It found that there are a host of serious problems that accompany illness, from lower earnings to unemployment. Medical bankruptcy, though, wasn’t nearly as common as anticipated, meaning that public policy aimed at fighting it might not have the anticipated results, either.