The graph is from recently published research by Cornell political scientist Peter Enns. The measure of public support for being tough on crime comes from averaging together 33 different questions about crime policy that have been asked repeatedly during this period.
The public’s rising punitiveness appears to be a fundamental determinant of the incarceration rate. In fact, if instead of becoming more punitive, the public’s support for being tough on crime had remained constant since the mid-1970s, the results suggest that there would be about 20% fewer people incarcerated today.