Can an Informative Letter Reduce Gun Crime and Be Cost-Effective?

A Study of Los Angeles

by Priscillia Hunt, Layla Parast, Gabriel Weinberger

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Research Questions

  1. Can a letter reduce gun crime?
  2. Should effects of the letter program be tested at the city level or the individual level?
  3. Can the benefits of the letter program outweigh the costs?

In 2007, the Los Angeles City Attorney's Office implemented a pilot study of a gun letter intervention to deter straw purchases and other illegal transfers of firearms, and to increase reporting of lost or stolen firearms. The intervention involved sending a letter to handgun purchasers during their ten-day waiting periods between purchase and taking possession of the firearm, which advised the purchaser that the new weapon was registered to them and that failure to properly record any transfer or loss of the weapon with California's Department of Justice could result in the owners' liability for any future misuse of the gun. A pilot randomized controlled trial of the letter program was conducted in two neighborhoods of the city of Los Angeles from May 2007 to September 2008.

Five years after the pilot study, the letter program was fully implemented citywide from January 1, 2013, through September 1, 2015. Letters were sent to all handgun purchasers residing in city of Los Angeles zip codes during the ten-day waiting period. Our study expanded on the pilot study, using two statistical approaches to assess the effect on firearm violence.

This report evaluates the effect of the letters sent by the Los Angeles City Attorney's Office on city-level rates of homicide, robbery, and aggravated assault with a firearm and conducts a cost-benefit assessment of this letter program.

Key Findings

Effects on Prevention

  • We were unable to detect a reliable citywide effect for the letter program on homicides, robberies, or aggravated assaults with a firearm.
  • While a statistical analysis would not have been able to identify the prevention of one or two crimes at a citywide level regardless of the true effects, it is also unclear whether the letter program can prevent any firearm violence.
  • One limitation of our methodology is that people could have transferred guns to individuals who committed gun crimes outside of Los Angeles, thus contaminating our control group.


  • The cost of the program was approximately $1.13 to $1.85 per letter, or $145 to $428 per day.
  • Considering the cost of the program relative to the societal benefits of preventing victimization, if the program prevents one homicide, one aggravated assault, or two robberies, then the program achieves a net benefit to society.

Statistical Approaches

  • For the short-term, time-series model, results suggest an immediate decline in firearms robberies after implementation of the letter program, but no such changes in aggravated assaults or homicides with a firearm.
  • Using the long-term, time-series model, results suggest no statistically significant effect on firearms robberies, but a statistically significant decrease of homicide with a handgun and aggravated assault with a firearm.
  • Because results are so highly sensitive to model specification, they are not robust enough to draw conclusions.
  • Similarly, a comparative case study approach was also used but did not identify a good enough statistical control group for Los Angeles to reliably analyze the effect of the letter.


  • Attorney's Offices should consider the trade-off between the relatively low cost of the letter intervention and yet relatively limited effect on city-level gun crime.
  • A better approach than analyzing aggregate, city-level data might be to conduct tests that are more sensitive to the effect of the letter intervention, such as an analysis based on gun-level data or a test for whether there are differences by subgroups based on characteristics of the gun purchase.
  • Another possible approach might be to study the data over a longer period with a long follow-up for testing the effects on crime, because it takes time for a gun to be used and to be recovered.

Table of Contents

  • Chapter One


  • Chapter Two

    Data on the Los Angeles Citywide Gun Letter Program

  • Chapter Three

    Gun Crime in the City of Los Angeles

  • Chapter Four

    How We Studied Effects on Gun Crime and Program Costs

  • Chapter Five

    Costs of the Gun Letter Intervention

  • Chapter Six

    Lessons on the Impacts of the Letter Program

  • Chapter Seven

    Can the Program Benefits Outweigh the Costs?

The research reported here was conducted by the Justice Policy Program within RAND Justice, Infrastructure, and Environment.

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