We are entering a divisive debate on the Supplemental Nutrition Assistance Program (SNAP), popularly known as food stamps. Unless facts drive the debate, it will be destructive as well.

Here are the basic facts: Food stamps reach their intended targets—poor and near-poor Americans. Over the past two decades, the program's overpayment rate has been cut by more than half to 3%, according to the U.S. Food and Nutrition Service. The large increase in the program's cost over the past decade mostly reflects worsening economic conditions...