Yes, Donald Trump deserves credit for putting immigration in the middle of the Republican presidential debate. But at the same time, Trump has focused much of the conversation either on side issues, like birthright citizenship, or on impossibilities, like the mass deportation of millions of illegal immigrants.

A more profitable debate might focus on issues raised in a new study from the Center for Immigration Studies, a group that favors limiting future levels of immigration. Under the wonky title “Welfare Use by Immigrant and Native Households: An Analysis of Medicaid, Cash, Food, and Housing Programs,” the study could form the basis of a new debate over the number and type of immigrants coming to the United States in years to come.