This story is mostly about racial disparity but a subtext is about private operators of contracted out prisons finding ways to leave more costly prisoners in the public system.  This phenomenon also arises in charter schools, many of which manage to have a “special education” population far below the public schools from which they are drawing students.  Competitive models for public services are one thing, but comparing public vs. contractor performance is a dishonest exercise if the game is rigged so that the privateers skim the cream.