Several observations (in this post) suggest that the role of legislative enactments in the state prison population increase was limited. Non-legislative factors that could explain the rise include, of course, the stunning rise in crime itself and discretionary responses to that rise by communities, law enforcement and the courts. However, parole board release decisions do not seem to be a likely factor.

Legislators respond with the tools that they have to public concerns and to troubling events. One can see, in the list of major criminal law enactments in this post, the history of punitive responses to recurring waves of legitimate public concern about drunk driving, drugs, guns, domestic violence, youth violence, sex offenses and crimes against the elderly.

From the early 1960s through about 1990, crime rose dramatically in Massachusetts. Most categories of crime have fallen since the early 1990s, but remain above their level in 1965. However, the state prison population has remained elevated, as the chart in this post (indexed to 1965 levels) demonstrates.