Police statistics are used to sway major policy decisions and channel billions of dollars in funding. The statistics can boost or undermine police legitimacy—an important predictor of crime. And they can be used by the public to force police departments to change their practices.
But the numbers are often incomplete or misleading.
Virtually all common statistics that deal with police work should only be used with major caveats, or at least with sufficient explanation, experts say.
“Data serves to researchers or to scientists in the same utility that a thermometer would serve a medical doctor,” said Alex del Carmen, professor and executive director of Tarleton State University’s criminology department. “No medical doctor using a thermometer will say that you’re dying from cancer if you read outside of 98.6.”
Data Collection
Most of the national police statistics are collected by the FBI and the Department of Justice (DOJ) through its Bureau of Justice Statistics (BJS).
But it’s voluntary for police departments to submit their data, as there are laws that prevent the federal government from interfering in states’ affairs.
Police departments serving 90 percent of the population do submit their data, which makes the FBI’s Uniform Crime Reporting Program the most comprehensive collection of statistical reports on policing.
However, the data is still incomplete. Cleveland, for example, didn’t report its 2015 numbers because of a problem with a new data collection system, yet the city has a violent crime rate more than three-and-a-half times the national average.
Furthermore, the FBI data only counts the most serious offense in every case. “If a burglary and a rape took place in the same incident, only the rape would be reported,” said del Carmen.
And even further, he noted, the FBI data only contains reported crimes, while the majority of crime goes unreported.
The BJS calls 90,000 households every year and asks people if they have been the victim of a crime in the past year.
The survey found that close to two-thirds of property crimes (burglary, theft, car theft) and almost half of violent crimes (rape, robbery, assault) went unreported in 2014.
According to the BJS survey, one in 50 people (age 12 or older) reported being a victim of a violent crime in 2014, whereas the FBI reported one in 267 people was a victim, based on 2014 crime rates.
The BJS survey is also limited: It excludes children under 12, the homeless, people in nursing homes, jails, and prisons, and murder victims.
Data on Police-Involved Homicides by Source
