Richard Matt and David Sweat, the escapees, may have imitated Andy Dufresne in “The Shawshank Redemption.” But no sane person would root for them — both murderers, Matt a charismatic psychopath — to end up free and clear in Zihuatanejo.

And while evil geniuses are pretty rare in our prisons, murderers are not.

Indeed, one of the key reasons the prison population rose so quickly prior to 2007 is that prosecutors were convicting more people for homicide, and putting them away for longer. The average time served for drug crimes rose very little from 1980 to 2010; the average time served for rape and robbery rose modestly. But the average time served for murder was just six years in the early 1980s; today it’s around 17 years.

At a certain point, then, sentencing reforms for nonviolent offenders will reach a natural limit, and we’ll confront a very different set of questions. Should sentences for rapists and (especially) murderers get ratcheted back down? Can alternatives to incarceration be implemented for violent offenders without a spike in crime and a political backlash? Or will reformers need to focus more on just improving conditions within prisons and accept that public order requires keeping a million-and-a-half Americans behind bars?