The title of this post is the title of this notable essay authored by Shawn Bushway. I recommend the full piece, and here is how it gets started:
The U.S. now incarcerates 25 percent fewer people than it did at its peak level of incarceration in 2009. Although this decline exceeds most projections from even 10 years ago, Stanford professor Keith Humphreys recently predicted in The Atlantic that even this smaller number would soon “fall off a cliff,” leaving us with a prison population that is 60 percent smaller than it used to be.
This decline has alarmed some people on the right, who believe we are now incarcerating too few people, rather than too many. All but the most extreme reformers accept that some number of people need to be incarcerated. The question then becomes, what is the optimal level for our society?
Ultimately, this question is not answerable scientifically. But there are some important trends in the current data that make me believe incarceration can (and will) continue to fall without any increase in crime. By the same token, any attempt to reverse the trend and incarcerate more people will not actually make us safer.