Former prisoners who violate the terms of their parole or probation supervision can be re-imprisoned without committing a new crime. This piece, by David Harding and Shawn Bushway, looks at how probation and parole violations contribute to the high rates of incarceration in the US, focusing on a study in which they, along with Jeff Morenoff and Anh Nguyen, followed every person convicted of a felony in Michigan from 2003 to 2006. Prisoners were followed through parole or probation violations, convictions for new felonies, and returns to prison over a five-year period. Then, the researchers compared the trajectories of those who were sentenced to prison and released on parole to those sentenced to probation.