This is the second in a series of blogs related to understanding who is incarcerated in Michigan prisons, why they are incarcerated, and for how long. The first blog addressed the first part of the question, of who is in prison; this blog is a general overview of the factors that impact Michigan prison population. There are several factors that affect prison population; intake, release and length of stay. Using the Michigan Department of Corrections’ March 2019 Prison Population Projection Report  we can better understand how these factors work together.


At the end of 2018, there were 38,761 people incarcerated in Michigan prisons, which is the lowest our prison population has been since the mid-1990s. At year’s end 2018, there were about 900 fewer individuals in Michigan prisons than the year prior. The decline in Michigan’s prison population is due to the release of individuals from incarceration being greater than intake into the system.

To understand the changing size of Michigan’s prison population, it’s important to keep in mind that the number of incarcerated people is affected by both the number of people entering the prison system and the number of people leaving it. In order to realize the greatest decreases in prison populations, the number of people entering the system have to be decreased, while the number of people leaving it have to be increased. Otherwise, for example, fewer people may be sent to prison on new sentences, but they may leave prison at a slower rate, resulting in a steadily growing population.


The largest category of prison intake is new court commitments, which accounted for 4,496, or 52 percent, of people sent to prison in 2017. However, this category has been steadily declining over the past five years. This is related to a drop in the number of felony dispositions, which means fewer people were charged with felonies.

The second category of intake relates to probation — either people who are sentenced to prison for violating terms of a probation sentence, or people sentenced to prison for a new offense committed while on probation. In 2017, 2,169 (25.1 percent) people were sentenced to prison for these reasons. As with new court commitments, probation-related commitments have also been declining. There has been a 50 percent decrease in this intake category since its peak in 2002.

Finally, parole-related commitments — such as violations of a parole agreement or new offenses committed while on parole — also accounted for the sentencing of 1,030 (11.9 percent) people in Michigan in 2017. This intake category has decreased 50 percent since its peak in 2008.


The complete information on how many people were released from prison in 2018 is not yet available. However, using the Parole Board Decisions Report released in January 2019, we can make some estimates. These reports are based produced quarterly, and the way that the quarters fall does not perfectly capture the year of 2018. Instead we have information from December 2017 through November 2018. In this 12-month period, approximately 9,300 people were granted parole, which is about 54 percent of people who had a parole hearing.

The other important part of this story is length of stay. Additionally, as discussed in prior blogs, and in the graph below, the majority of people in Michigan prisons have relatively short sentences, but the state had an average prison sentence length of 10.3 years in 2017, not including those who have minimum sentences of life.

A significant portion of people in Michigan prisons are there for a long time — about 10,000 people, or a quarter of our population — has a minimum sentence of 20 years or more. So, while reducing the number of people who are entering prison is one way to reduce the prison population, it is not the only way, and it will only go so far. The number of individuals serving these long sentences is growing faster than it is being released and they are getting more expensive to care for with each passing year.

Future blogs will further delve into the issues of long prison sentences and what can be done to further reduce the number of individuals incarcerated in Michigan.

*Percentages may not equal 100% due to rounding

**Life sentences included in 20 years or more group



~ Anne Mahar
Research Specialist