Impact
A small number of large U.S. cities drove average crime trends from 2018-2022
Objective
To determine differences in recent violent crime-rate trends across U.S. cities of varying sizes nationally in response to a spike in such crimes, particularly murder, in 2020.
Approach
Analyze population rates of four types of violent crime over the years 2018 to 2022 using group-based trajectory modeling (GBTM) and a sample of 590 U.S. municipalities with populations of 25,000 or more.
Impact
A minority of U.S. cities that had relatively high rates of some types of crime such as murder prior to 2018 reported sizable increases during the study period, which drove average trends. Most municipalities reported smaller increases. This suggests that cities with the highest crime rates should receive the resources necessary after national events are likely to increase criminal activity.
The United States experienced a significant overall increase in some violent crimes, including murder, during the COVID-19 pandemic. This increase is likely partially attributed to stay-at-home orders and other prevention measures implemented during the pandemic, coupled with criminal justice challenges and social unrest in the wake of the murder of George Floyd.
Importantly, a close examination of violent crime trends in a recent RTI study reveals that national changes in crime are largely driven by a small proportion of large U.S. cities, with most municipalities reporting little change in crime rates between 2018 and 2022.
Our Research Methods and Results
The study analyzed violent crime data for the years 2018 to 2022 from 590 U.S. cities of 25,000 people or more. We examined records from the Federal Bureau of Investigation’s (FBI) National Incident-based Reporting System (NIBRS), which is used by law enforcement agencies to report crimes, and analyzed the data using a statistical method called group-based trajectory modeling (GBTM).
We used this data to test whether groups of cities experienced unique crime trajectories during the 2018-22 period. We focused our analyses on murder, aggravated assault, robbery, and carjacking.
The results are as follows:
Murder: 446 cities, or 76 percent, are characterized as a “low stable” trajectory. This group averaged a murder rate of approximately 0.40 per 100,000 per quarter in 2018-19, with only a slight increase to about 0.50 per 100,000 per quarter in 2020-22.
The remaining 144 cities (24 percent) can be characterized as “high increasers,” with an average 2.5 murders per 100,000 at the beginning of the study, increasing to an average of 3.8 in 2020-21, then decreasing slightly to 3.5 in 2022.
Aggravated Assault: Of the 590 cities in the study, 395 (68 percent) are identified as “low stable,” 150 cities (26 percent) are considered “middle increasers,” and 38 cities (7 percent) are “high increasers.”
The low stable cities began with a relatively low rate of approximately 27 aggravated assault incidents per 100,000 people in 2018, increasing slightly to 31 per 100,000 from 2020 to 2022.
Middle increasers began with 91 per 100,000, with a small increase to 105 per 100,000. High increasers had begun with a relatively high rate of 193 per 100,000 and experienced a relatively significant increase to 233 per 100,000 in 2020-22.
- Robbery: There was an overall decline in incidents of robbery during the study period. Of the 590 cities in the study, 360 (61 percent) are described as low stable, decreasing from approximately 8.3 to 6.5 incidents per 100,000 during the study period; 191 cities (32 percent) are described as “middle decreasers,” decreasing from 32.1 to 25.5 incidents per 100,000; and 39 cities (7 percent), were characterized as “high decreasers,” with a relatively high number of 86.9 percent per 100,000, decreasing to 68.4.
- Carjacking: Two trajectories were identified for carjacking rates. Of the 590 cities, 455 (77 percent) are characterized as “low increasers,” beginning with quarterly rates of approximately 0.37 per 100,000 with a slight increase to 0.57 per 100,000. The remaining 135 cities (23 percent) are described as “high increasers,” with a beginning rate of 3.3 per 100,000 and increasing to 4.1.
An Uneven Increase in Crime Rates Across Cities
The results of our study show that the increases in murder, aggravated assault, and carjacking rates and the decrease in the robbery rate that occurred in 2020 are related to prior crime levels of the 590 municipalities in the study.
Cities with the highest crime rates prior to 2020 saw the highest increases during the 2018-22 study period. In addition, cities with the lowest crime rates during the same period experienced little to no difference.
These results suggest that while it may appear that violent crimes such as murder and assault increased dramatically across the United States in 2020, these numbers seem to be driven by a relatively small number of large cities that already had high rates and saw them jump drastically that year.
It is important to remember that the 590 cities sampled in this study are not nationally representative, but they do represent a substantial segment and should inform future research on violent crime trends in the United States.
Preventing Future Violence
Policymakers should consider these findings as they craft crime and violence prevention legislation. The study offers evidence that directing resources at cities that have historically experienced the highest violent crime rates would prevent trauma and loss of life.
