It’s been noted before that the upswing in Americans on food stamps and the continued struggles of Millennials after the recession have helped dollar stores find footing. But with Pew Research noting that just 50 percent of U.S. wealth is held by middle-income households — compared to 61 percent in 1973 — a rash of retail closings and the decline of malls in middle-class areas has swept more people toward dollar stores.