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The key lesson from the available data is that the problem does not represent a widespread change in anti-social or criminal behavior in general, but rather a narrower challenge of gun crimes committed in public places, frequently by young people—adults as well as teenagers—in our city’s most distressed neighborhoods. While this report is intended to present just the facts, our goal is to inform the ongoing conversation about how the city can reverse this trend and keep all city residents safe. We will continue to partner with the city and civic community to share, help implement, and evaluate (when possible) the most promising solutions, and aim to share our current thinking and best ideas in other venues in the future. Motivation for focusing on monthly year-to-year changes to track the increase in gun violence Because gun violence follows a seasonal pattern—higher in the summer, lower in the winter— we focus on monthly year-to-year changes to isolate trends over time in the data from regular seasonal changes in violence that occur every year. That is, by comparing rates of gun violence in each month of the year to the rate of crime in the same month in the prior year, we can avoid confusing changes in trends with seasonal effects. To see why this is important, consider the number of homicides in each month of 2014 and 2015. As one can see in the figure below, homicides began to increase in the spring of 2015 and into the summer. Focusing just on those month-to-month changes over the course of 2015 might lead to a conclusion that something in the winter or spring of 2015 (e.g., the cut in state funding to Cure Violence in March 2015) contributed to the subsequent increase in homicides. But the figure below also shows that a similar increase in homicides occurred in 2014 as the temperature increased; that is, at least part of the homicide increase that occurred after March 2015 was due to the normal seasonal pattern that we see every year. The figure below shows that, for a few months over the summer, homicides in 2015 were indeed above their levels in 2014, but by the fall, October, November, and December of 2015 looked very similar to the same months in 2014. There does not appear to have been any change over the course of 2015 that caused a sustained increase in lethal violence in the city.