How many people should be in prison?

Kahryn Riley, Mackinac Center for Public Policy

It’s common to have a conversation about criminal justice reform that includes an anxious reference to the “mass incarceration crisis.” But as legal academic John Pfaff points out in his new book “Locked In,” the phrase might actually be meaningless because we don’t know the right number of offenders to incarcerate. For instance, there are 43,000 people occupying Michigan prisons right now. Is that “mass incarceration?” If so, what is “normal incarceration” and how do we get there? There’s no clear answer to these questions, but here’s how to approach about the issue.

First, determining the “right number of people” metric is influenced by your point of view on more fundamental criminal justice questions. If you’re a prison abolitionist who believes prisons are innately corrupting and harmful to society, your “right number” metric is practically zero. But if you’re a “tough-on-crime” proponent who sees long sentences as an effective means to deter criminal activity, your “right number” would be much larger.

Second, while reformers across the spectrum tend to agree that the incarceration rate is too high, there is no consensus on how to scale it back. And here is where the complexities of the problem of calculating the right number of offenders to incarcerate start to appear. Dozens of variables contribute to the size of the prison population, and they are all quite difficult to measure.

Take the idea of justice, for example. The state punishes offenders on behalf of their victims, but it’s not always clear what sentence will produce the appropriate amount of justice. If a store is robbed, is justice served to the store owner if the offender is given a two-year sentence or five-year sentence? Compounding the problem is the fact that plea bargaining introduces even more uncertainty about how long — or even whether — any given offender will serve time. Is justice served when pleas are bargained down?

This uncertainty persists at every level of the criminal justice system. Once the offender enters prison, it is true that incarcerating him averts any crimes he might have otherwise committed, but we should always ask: Is this the most effective way to improve public safety or are there better alternatives? We have no way of counting the averted crimes, and some research suggests that incarcerating people for too long may induce them to commit crimes later that they otherwise might not have committed.

Decisions about when and how a person can be released from prison are also fraught with complexity. Michigan’s “truth-in-sentencing” policy means that a prisoner will serve every day of the minimum sentence imposed by the judge at trial. But, after that, it’s up to the parole board to decide whether and when to release a prisoner before he has served the maximum statutory punishment for his offense. What factors should the board take into account in making the release decision? Is there some point after which keeping a prisoner incarcerated will do more long-term harm than good? Should we expect imprisonment to reform convicts or just mete out punishment?

Finally, budgetary concerns often impact all of the issues raised above. If the price tag gets too high, the question must shift from the right number of offenders to incarcerate to the right type of offender to release, which is a different question that requires a different analysis. The state only has so much money and how much to spend on the criminal justice system is up to legislators who have competing priorities to consider.

All of these factors and more influence the size of the prison population and should be accounted for in discussions about how to determine the optimal number of prisoners. Questions about how well and when prison works and weighing that against other budget constraints is difficult. But understanding these and other factors at work in the criminal justice system is crucial to resolving not only our collective concern about the size of the prison population, but also every other perceived inefficiency or idea for improvement.


Kahryn Riley is a Mackinac Center policy analyst. She joined the criminal justice reform initiative in June 2016, after working for two years as a regional advancement officer at the Center. Riley is an attorney and an alumna of Hillsdale College and Regent University School of Law.