“Why Prisons Are Shrinking” (editorial, Oct. 28) laid out why data-driven policies are causing state prison populations to shrink. Unfortunately, the same cannot be said of the federal prison system, which continues to contract with private prison corporations to facilitate its expansion. The federal prison system added nearly 1,500 prisoners last year. Behind this growth is a sharp rise in criminal prosecutions of immigrant border-crossers over the past decade. Before the 2005 implementation of Operation Streamline, immigrants were typically processed through the civil immigration system. Now they are funneled, often en masse, into the criminal justice system. In fact, for the past four years, more people have been convicted of immigration offenses than any other type of federal offense. Taxpayers are on the hook for the bill. My organization estimated in a report last fall that the federal government now commits over $1.02 billion per year toward the criminal incarceration of migrants for immigration offenses.