Frequently Asked Questions

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About the Tool

What does Arrest Trends do?

Arrest Trends allows users to easily access and visualize decades of policing data–including arrests, demographics, clearance rates, victimizations, and data reported–that were previously scattered across different locations and were difficult to interpret.

How does Arrest Trends work?

Arrest Trends draws from a wealth of publicly available but disparately located policing data, sourced primarily from the Federal Bureau of Investigation’s (FBI’s) Uniform Crime Report (UCR), the Bureau of Justice Statistics’ (BJS’s) National Crime Victimization Survey (NCVS), and the U.S. Census Bureau’s (USCB’s) Populations with Bridged Race Categories. Vera researchers restructured, aggregated, and merged these datasets for integration into Arrest Trends.

Why was Arrest Trends developed?

Information about arrests–such as how often it is used, what it is used for, whom it is used on, and how effective it is at preventing and solving crimes–is needed to understand and advance policy and practice. While evidence is lacking in many areas, illuminating data exists that can begin to answer many of these questions. The government invests considerable resources to capture information surrounding many policing indicators, including civilian-police interactions, arrest and clearance rates, law enforcement operations, crime and victimization, and more. Yet, due to data complexities, these key indicators are often inaccessible to those who could most benefit from them: practitioners, policymakers, advocates, researchers, journalists, and philanthropists. In response to this need, the Vera Institute of Justice (Vera) developed Arrest Trends–unlocking this important knowledge.

How is Arrest Trends different from other tools that use similar data?

To date, several resources exist to aid in the analysis of policing data. These tools are beneficial in that they are efficient, relatively easy to use, and often interactive. They remain limited, though, in the following ways:

  • Users looking for comprehensive information on arrests must consult multiple resources.

  • Few tools offer drill-down features that allow for analysis at the national, regional, state, county, and agency levels.

  • Outputs are numbers-heavy and are often presented without written explanations or clear visualizations, making it difficult for users to interpret the findings.

  • Tools currently offer no means for comparing Arrest Trends across similar agencies or locations.

  • Agencies that report partial data are excluded from the majority of tools, affecting the data’s accuracy and completeness.

  • Rate calculations (such as clearance rates, arrest rates, and arrest rates for specific demographic groups) based on resident populations are largely absent.

  • Although tools are interactive, they often cannot answer specific or complex research questions.

One centralized and highly interactive tool is needed, through which users can explore and understand comprehensive Arrest Trends at both the national and local levels. Vera designed Arrest Trends to meet this need.

Who developed Arrest Trends?

Arrest Trends was developed by the Vera Institute of Justice’s (Vera’s) Policing Program. The research team responsible for its creation would like to acknowledge Nick Turner, Susan Shah, Mary Crowley, and Jim Parsons for their invaluable support and guidance throughout the development of Arrest Trends. We are also grateful for the assistance given by Vera colleagues: Jackson Beck, Alex Boldin, Léon Digard, Chris Henrichson, Oliver Hinds, Jacob Kang-Brown, Mawia Khogali, Chris Mai, Michael Mehler, Cindy Reed, Karina Schroeder, Kinsen Siu, Ram Subramanian, and Hayne Yoon. In addition, we are grateful for the assistance given by Vera’s Policing Fellows and Interns: Kristyn Jones, Matthew Stock, Vanessa D’Erasmo, and Darren Agboh. Special thanks to our external advisor, Ross Dakin for his expertise and valuable advice. We would like to thank Teal Media, Gramener, Inc., Civic Hall Labs, and Delta.NYC for their contributions in developing Arrest Trends. Finally, this project would not have been possible without the support of Vera Institute of Justice’s Capital Campaign; Elizabeth Grossman, Kevin Miller, and all of the Microsoft Cities Team; and Brianna Walden, Jordan Richardson, and all of the Charles Koch Foundation.

Contact Information and References

Who can I contact with general questions or potential concerns about the data?

Please send any inquiries to ArrestTrends@vera.org.

How do I reference this tool?

Vera Institute of Justice. Arrest Trends. Last modified January 2019. www.arresttrends.vera.org.

About the Data

Where does the data come from?

Arrest Trends is populated with data from the following data series:

  • Uniform Crime Report (UCR): Arrests by Age, Sex, and Race;

  • UCR: County-Level Detailed Arrest and Offense Data;

  • Arrests Data Analysis Tool National Estimates;

  • U.S. Census Populations with Bridged Race Categories;

  • UCR: Offenses Known and Clearances by Arrest;

  • National Crime Victimization Survey (NCVS) Victimization Analysis Tool;

  • Federal Bureau of Investigations (FBI) Offenses Known to Law Enforcement; and

  • Law Enforcement Agency Identifiers Crosswalk.

To learn more about the data available within Arrest Trends, see Data Sources and Methodology. To learn more about where you can access these data series, see Resources.

How reliable are the data?

Police agencies report data to the UCR on a voluntary basis. Because Vera did not collect the data and is instead publishing and aggregating existing publicly available data, any errors in primary data sources will be repeated here. If you see an error and would like to have it corrected, please contact ArrestTrends@vera.org.

Can I download the data?

Arrest Trends does not currently support dataset downloads. Vera anticipates releasing this feature in future updates to the tool.

What years are available?

ears of data available differ by indicator. Data for the arrests, demographics, and data-reported indicators generally spans from 1980 to 2016. Data for the clearance-rate indicator spans from 1964 to 2016. Data for the victimization indicator spans from 1993 to 2016. More specifics about the data and respective time ranges available within Arrest Trends can be found in Data Sources and Methodology.

How far can I drill down using this tool?

Most of the data within this tool can be observed at the police-agency level. County, state, regional, and national data are also available.

What is the difference between reported data and estimated data?

For a variety of reasons, not all agencies report their data completely–or even at all–which can cause issues such as undercounting. (To learn more, see Data Sources and Methodology.) To account for this, the FBI provides two sets of UCR data: estimates and reported data. For a more complete picture that adjusts for underreporting, users can opt to view estimated data. To examine trends in the data exactly as reported to the FBI and to avoid any potential challenges with data accuracy that may be caused by estimating nonrandomly missing data, users can opt to view reported data.

What offense types are featured in this tool, and how are they defined?

As classified by the FBI, Part I (serious violent and property) offenses, Part II offenses, and the FBI’s 29 individual crime types are featured in this tool. For a complete list of the crime types featured in this tool along with their definitions, see Data and Methodology Appendix A, Appendix B, and Appendix C.

What is a clearance rate?

According to the FBI, crimes are considered cleared by arrest (i.e., “solved”) when: “at least one person is: a) arrested; b) charged with the commission of the offense; and c) turned over to the court for prosecution (whether following arrest, court summons, or police notice). Although no physical arrest is made, a clearance by arrest may also be reported when the individual is a person under 18 years of age and is cited to appear in juvenile court or before other juvenile authorities.” Clearance rates, then, are the percentage of offenses known to law enforcement that are cleared by arrests.

How are clearance rates calculated?

Clearance rates are calculated as the volume of crimes solved by arrests compared to the volume of offenses known to the police. Clearance rates are important to explore, as they can indicate police-community collaboration and police effectiveness. However, clearance rates of 0 percent or 100 percent should be interpreted with caution, because these may indicate data-entry errors, missing data, or the presence of arrest clearances that pertain to offenses known from previous years.

How are arrest rates calculated?

All Arrest Trends arrest rates are calculated as the number of arrests per 100,000 residents. The tool presents two forms of arrest rate: reported and estimated. Vera calculates reported arrest rates for agencies that reported at least partial data, using the population sizes indicated in the UCR data series. Vera calculates estimated arrest rates using population sizes indicated in the UCR data series for all agencies in that geographic unit (county, state, region, or nation) regardless of whether they reported any arrest data. Estimated arrest rates for specific demographic groups are calculated using the population sizes indicated in the U.S. Census Populations with Bridged Race Categories data series. Arrest rates 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, because not all people are residents of the place where they were arrested and virtually no arrests are made of young people under age 13, which may skew rates in places with particularly young populations.

What data should I interpret with caution?

Arrest rates and clearance rates should be interpreted with caution. Arrest rates should be interpreted with caution because not all people are residents of the place where they were arrested and because virtually no arrests are made of young people under age 13, yet all age ranges are included in these figures (due to data collection methodologies), which may skew rates in places with particularly young populations. Clearance rates of 0 percent or 100 percent should be interpreted with caution, because these may indicate data entry errors, missing data, or the presence of arrest clearances that pertain to offenses known from previous years.

Why can't I select and explore certain demographic groups?

When agencies report arrest data to the UCR, they are required to specify arrestees’ age range and gender. Reporting arrestees’ race and ethnicity (the categories specified by the UCR are further broken down to distinguish between juveniles and adults) is optional. Likewise, based on UCR’s data-collection practices, only certain cross-sectional demographic groups can be observed. Further, data on ethnicity were only collected and featured in UCR from 1980 to 1991, making this information unavailable for all other years.

If UCR reporting is voluntary, does Arrest Trends allow me to understand and explore trends in underreporting?

By exploring the “Data Reported” indicator, you can learn more about the gaps in available policing data and how these vary by time, place, and data type. Because the UCR program instructs agencies to report their data based on which month it occurred in, missing and incomplete data can be detected based on how many months are nonexistent within the series. In other words, agencies with 12 months of data reported complete data, agencies with one to eleven months of data reported partial data, and agencies with zero months of data reported no data. For this reason, throughout Arrest Trends, you will see indicators of how many months of data were reported–a useful marker of data completeness (i.e., degree of underreporting).

Why am I seeing drastic changes in rape-related Arrest Trends around 2013?

The FBI changed its definition of rape in 2013. Beginning in 2013, police agencies could report data according to either the new or old rape definition. Because of the discrepancies in reporting, rape-related offenses are not available in estimated datasets after 2012.

Why am I seeing drastic changes in victimization volumes around 2006 and 2016?

In 2006 and 2016, NCVS underwent redesigns in its sampling methodology. You should be cautious when comparing data observed in these years to other years.

Understanding and rectifying missing data

Why can't I find my police agency or community?

UCR reporting is entirely voluntary–agencies can choose to report all of their data, some of it, or none of it. Agencies that do not report any of their data to the UCR are not featured in this tool (although if you’re still interested in learning about their Arrest Trends, Vera encourages you to try visiting their departmental or jurisdictional websites, as similar data may still be publicly available there). To circumvent undercounting issues caused by voluntary reporting practices, the FBI also releases UCR series that contain estimated data at the county, state, region, and national levels. For this reason, you are encouraged to explore your county, state, or region’s estimated data, especially if your individual agency is not present within the tool. Separately, the UCR data series sometimes uses acronyms or abbreviations to identify agencies. Before determining that your agency is missing, try using the tool’s “Browse by Location” feature to filter by geographic location, and see if it exists under another name or enter the jurisdiction or agency name. Note also that cities and towns are not explicitly featured within Arrest Trends at present, because police agencies’ jurisdictions do not always reliably correspond to these geographic units. Instead of searching by a city or town, try searching by police agency or county name. If you still believe data are missing in error or would like to include data that have not been previously reported, please contact ArrestTrends@vera.org.

I work for a police agency, and the data in the tool do not match our reports; can I fix this, and how?

Policing data–especially clearances–are dynamic. For example, an arrest made in 2016 for a crime that occurred in 2014 technically counts as a 2014 clearance. Likewise, agency data are constantly changing. UCR data are typically static outside of annual updates, meaning that agency records may differ if something changed after reports were provided to the FBI. If you represent an agency and would like to fix incorrect data, please contact ArrestTrends@vera.org.

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