New ‘Base Rate’ Data Predicts Individual Likelihood of Arrests, Charges, Incarceration

Top five and bottom five average base rates for any type of arrest from 2000-2020.

Source: Criminal Justice Base Rate Project.

Highlights

• Unlike traditional crime rates, which measure crime incidents, base rates calculate an individual’s likelihood of interacting with the criminal justice system.

• A University of Nebraska at Omaha-led team launched an interactive dashboard that can help stakeholders make more informed decisions and forecast the impact of criminal justice policy.
• Lead researcher Zachary Hamilton, Ph.D.: “The findings from this study are a major shift in how we understand justice system involvement...This will be a valuable tool for stakeholders to make more informed, decisions that address the unique needs and disparities within their communities.”

For the first time, policymakers, advocacy groups, and citizens have access to a national database that can estimate the average person’s likelihood of interacting with the criminal justice system.

While crime rates have been used for decades to identify crime trends in a given area, the Criminal Justice Base Rate Project (CJBRP) provides a state-by-state estimation of the average person’s likelihood of being arrested, charged, or incarcerated.

Led by Zachary Hamilton, Ph.D., a University of Nebraska at Omaha (UNO) School of Criminology & Criminal Justice Professor and Associate Director of the Nebraska Center for Justice Research, a team of researchers studied 20 years' worth of data to provide valuable insights into how demographic and regional differences shape criminal justice system outcomes.

Transforming Criminal Justice Insights with Base Rates

The team’s findings culminated in the CJBRP, an interactive dashboard that allows users to delve into the data by choosing different factors—such as race, gender, and location—to better understand the individual probabilities of arrest, charges, and prison admissions. The data can serve as a critical tool for developing targeted programs and policies that address the unique challenges faced by different communities.

“The findings from this study are a major shift in how we understand justice system involvement,” Hamilton said. “By focusing on base rates, we’re able to, not just examine crime trends, but how likely individuals from different backgrounds are to encounter the justice system. This will be a valuable tool for stakeholders to make more informed, decisions that address the unique needs and disparities within their communities.”

The report states that “Similar to the U.S. Congress’ use of the Congressional Budget Office prior to enacting key legislation, stakeholders may use base rates as a method of forecasting the future impacts of bills under consideration” and that “these forecasts have the potential to project the downstream effects driving resource needs from one justice system to another.”

Key Findings on U.S. Base Rates for Arrest, Charges, and Incarceration

Several key findings about arrest, charge, and incarceration base rates between 2000 and 2020 emerged from the study, including:

• National arrest rates saw a sharp decline: The national arrest base rate fell by more than 50%, from 6.15% in 2000 to 3.21% in 2020, with a sharp 25% decline in 2020 alone, attributed to COVID-19-related policy changes.

• Charge rate trends fluctuated: The charge base rate increased from 2.20% in 2000 to 2.65% in 2006, before decreasing to 0.72% by 2020. This trend aligns with federal arrest and charge patterns during the same period.

• Prison admissions peaked and declined: The U.S. prison admission base rate reached its peak at 0.34% in 2007, but steadily declined over the following years, reaching 0.13% in 2020—a decline accelerated by COVID-19 policies.

• A sharp decrease for male arrests: Men experienced a significant drop in arrest base rates, from just over 11% in 2000 to 4.9% in 2020, whereas women’s arrest rates only decreased by about 1% over the same period.

• Racial disparities in arrests shrank: In 2000, Black individuals had a 17.7% likelihood of arrest compared to 5.3% for White individuals, making Black individuals more than three times more likely to be arrested. By 2020, this gap narrowed to 6% for Black individuals and 2.9% for White individuals.

• Racial disparities in prison admissions shrank: The prison admission rate for Black Americans declined from 0.9% in 2000 to 0.5% by 2020, while the rate for White Americans remained relatively steady at around 0.2%.

• Prison admissions for drug offenses saw a steep drop: The prison admission base rate for drug offenses dropped by nearly 30% between 2008 and 2012, reflecting broader shifts in policy and law enforcement focus on non-violent offenses.

• Regional trends converged: The Western U.S. saw the largest reduction in arrest rates, falling from 8% in 2000 to 4% in 2020. By the end of the study, arrest rates across all regions ranged from 2% to 8%, indicating a convergence in regional trends.

• Charges for young and middle-aged adults decreased: In 2007, more than 5% of individuals aged 18-24 were charged with an offense, but by 2020, this rate dropped to below 2%. For those aged 35-44, charges decreased from approximately 2% to less than 1%.

• Arrest rates for Black individuals in the South decreased: In Southern states, the arrest rate for Black individuals decreased from nearly 13% in 2000 to approximately 6% in 2020, showcasing significant changes in justice involvement across regions and demographics.

Researchers also stated in the report their intent was to “provide a new source of data, not provided through common metrics of criminal incident reporting” and that the findings will "change the field’s understanding of crime accounting metrics, providing what we hope is a more useful understanding of the average citizen’s likelihood of offending.”