More than 39 million American adults incurred at least one fee for overdrawing their bank account or having insufficient funds in the past 12 months, according to an analysis of survey data by The Pew Charitable Trusts. Most of these consumers, known as overdrafters, view bank overdraft programs as a way to ensure that payments will go through if checking account balances are low. But almost a third—representing more than 12 million people—said doing so is a way to borrow when short on cash.