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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.

Costs

• 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.