The voices of Urban Institute's researchers and staff
October 1, 2018

What we learned from forecasting state prison populations

October 1, 2018

Using the Urban Institute’s new Prison Population Forecaster, anybody can see how the prison population in nearly every state will look if current practice goes unchanged and can model the effects policy changes could have on racial disparities, costs, and the size of the prison population.

This tool uncovers some often-overlooked take-aways to guide criminal justice reform.

There is no one-size-fits-all solution for reducing the total number of people in prison. Every state has its own factors and challenges that contribute to mass incarceration.

In Arizona, reducing admissions for drug offenses by 50 percent would lead to an 11.7 percent decrease in the state’s prison population by 2025 compared with baseline projections. In California, this would create just a 1.5 percent decrease.

Penalties for violent and other serious offenses are a major driver of state prison populations.

Because of the “stacking effect,” these policies lead to long sentences that inflate prison populations, have a dubious impact on public safety, and carry many collateral consequences.

To reduce the size of their state’s prison population, policymakers and other stakeholders must consider strategies to address prison terms for serious offenses.

In Minnesota, halving the length of prison terms for violent offenses would cut the population by nearly 25 percent by 2025, while a similar reduction for property offenses would only lead to a 5 percent decrease.

In every state, even significant cuts to the number of people in prison and within individual offense categories does little to reduce the proportion made up of people of color.

Decarceration efforts that seek to advance racial justice must include targeted strategies focused on reducing disparity throughout the criminal justice system.

Large reductions in a state’s prison population correspond to significant savings in correctional spending, which can make resources available for other public safety priorities, such as crime prevention.

Conversely, policies that increase the prison population can increase a state’s correctional spending. Increasing admissions to prison for drug offenses by 50 percent would add $83.7 million to Illinois’s correctional budget and $150.1 million to Texas’s.

Reform must be grounded in data and evidence to achieve its goals.

Advocates and policymakers need tools like the Prison Population Forecaster to understand opportunities to improve the criminal justice system in their state. We encourage you to explore the tool to see what drives the prison population in your state and chart your own path to reform.

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As an organization, the Urban Institute does not take positions on issues. Experts are independent and empowered to share their evidence-based views and recommendations shaped by research.