Can it really be true that most people in jail are being held before trial? And how much of mass incarceration is a result of the war on drugs? These questions are harder to answer than you might think, because our country’s systems of confinement are so fragmented. The various government agencies involved in the justice system collect a lot of critical data, but it is not designed to help policymakers or the public understand what’s going on. Meaningful criminal justice reform that reduces the massive scale of incarceration, however, requires that we start with the big picture.