Interpreting arrests data
Police enforcement takes many forms including citations, summonses, warrants, arrests, and more. While national-level data do not yet exist for the majority of these indicators, detailed arrest data do exist through the FBI’s Uniform Crime Report (UCR) persons arrested tables. The UCR is a large and complex data series that, in part, culminates all of the arrest data voluntarily reported by each of the country’s 18,000+ police agencies. On this page, users can learn more about the wide reach of police enforcement by interacting with a series of visualizations that explore how arrest trends vary by offense type, time, and place.
More specifically, UCR datasets are broken down by the month in which an arrest occurred. As such, agencies can opt to report none (i.e., zero months), some (i.e., 1-11 months), or all (i.e., 12 months) of their data. Hover over the visuals below to see how many months of data were actually reported. Note that months reported was calculated and validated using publicly available data, which may not reliably a) indicate when multiple agencies report their data together, or b) specify months in accordance with UCR reporting instructions. Alternatively, to avoid issues of undercounting, users can opt to view FBI estimates—available at every geographic level except agency. Based on UCR data availability, users can explore reported and estimated arrest trends at the national level from 1980-2016 (slight variations from this time range exist at the county, state, and regional levels where, for example, estimates span from 1977-2014 and are missing 1993). Data are labeled as “not applicable” when relevant information was not collected in a given year, and “missing” when relevant information was collected but a location did not report it. Lastly, rarely occurring errors present in UCR datasets (for example, an agency mistyping “1,000 arrests” in their UCR report when “100” actually occurred, or a true instance of missing data being misclassified as “0 arrests”) may also be present in this tool.
- Arrest Rate
Arrest rates are calculated based on UCR arrest volumes and population sizes. These figures are helpful in comparing relative trends across geographic units, and over time in instances where population sizes have changed. However, arrest rates should be interpreted with caution, as not all people are residents of the place where they were arrested and virtually no arrests are made of youth under age 13, which may skew rates in places with particularly young populations. To learn more, see Data Sources and Methodology.