Explaining the Great 2020 Homicide Spike
Last year, cities across the country suffered from what I will call the Great 2020 Homicide Spike. Homicide rates were 30% higher than in 2019—an historic increase representing more than 1,268 additional murders (in a sample of 34 cities), according to an important new report released today by Professor Richard Rosenfeld and two colleagues. The new Rosenfeld report explains that this is a “large and troubling increase that has no modern precedent.” The previous largest single-year increase in the United States was 12.7%, back in 1968.
After presenting data on the homicide spike, the Rosenfeld report briefly attempts to explain what might have caused it. The report discusses two potential causes: first, the COVID-19 pandemic; and, second, anti-police protests following the death of George Floyd during his arrest by Minneapolis police. But after carefully laying out these two possibilities, the report declines to take a position on which one is the more significant contributor to the homicide spikes. And then, in a concluding section on recommendations, it focuses on need for subduing the COVID-19 pandemic and downplays the need to consider whether the anti-police protests—and consequent police pullbacks—have played a major role in the deaths of more than a thousand homicide victims.
In my view, the best explanation for the Great 2020 Homicide Spike is a decline in proactive policing–and, accordingly, public policy responses to the spike should specifically address that decline. This post builds on a lengthy paper I published last month in the Federal Sentencing Reporter (which also included responses from Larry Rosenthal and Richard Rosenfeld). My paper relied on data through the summer of 2020, but my position can now be supported with data ending through the end of 2020 based on the new Rosenfeld report.
Let’s start first with 2020 homicide data, as no real dispute exists about the fact that last year homicides increased dramatically in most major cities. The report looked at homicide rates in 2020 compared to 2019 in sample of 34 cities. In 29 of the 34 cities, homicides increased–and, in many cities, increased substantially–as shown in Figure 11 from the new Rosenfeld report:
As can be seen, there were significant increases in almost all cities. Because these figures are percentages, however, they can perhaps be misleading for smaller cities. As the report explains, Chula Vista, California, experienced the largest percentage homicide increase in the sample (150%), but that percentage is based on a difference of just six homicides (ten in 2020 compared with four in 2019).
But staggeringly large homicide increases were observed in many of the country’s most populous cities. New York suffered 131 homicides, representing a 43% increase. Chicago suffered 278 homicides compared to its 2019 total of 502, for an increase of 55%. Los Angeles’ homicides were up 37%, Phoenix’s up 46%, Philadelphia’s up 27%, Milwaukee’s up 85%, and Seattle’s up 63%. Unsurprisingly, given their size, large cities with appreciable homicide increases contributed disproportionately to the overall increase in murder victims. The nation’s three largest cities (New York, Los Angeles, and Chicago) accounted for 40% of the 1,268 additional people murdered in 2020.
While variation exists among the cities, what is most notable is that homicides rose substantially in the vast majority of them. As the Rosenfeld report appropriately concludes: “[L]ocal variations in social and demographic conditions, while important, do not appear to be the primary driving force behind rising homicide rates. National factors must be explored to better understand the increase.”
The report then turns to two national factors that might have caused the Great 2020 Homicide Spike: (1) the pandemic; and (2) protests against police violence. Turning first to the pandemic, the report argues that the pandemic may have initially suppressed some homicides by limiting the opportunities for offenders and victims to interact due government-ordered restrictions. Then, as pandemic-related restrictions were relaxed during the last spring and summer of 2020 (or compliance with them diminished), homicide rates increased. The report suggests that this increase in social mobility was a major factor in the homicide surge, although the report does not include precise data or findings on social mobility.
A major problem with attempting to link the homicide spike to the pandemic itself, however, is the spike’s timing. Let’s first look at the homicide trend line that needs to be explained. The new Rosenfeld report provides this graph of homicide trends from 2017 through 2020:
This graph depicts a structural break in homicide trends (the vertical red line) occurring in June 2020 that might appear to correspond somewhat to the onset of the pandemic and related social mobility trends. But this graph–which depicts monthly data–does not allow much precision in identifying when the spike in homicides began. To be sure, homicides increased in the spring of 2020. But given the “seasonality” of homicide (more homicides in summer, fewer in the winter), some general upward trend would be expected.
More informative on the issue of the homicide spike’s precise timing are weekly homicide data, reported though October 2020 by Rosenfeld in an earlier report, as depicted below:
This graph depicts the structural break (the vertical red line) in homicide trends–i.e., a statistically significant change in the times series occurring in the last week of May. This graph would seem to identify the increase in homicides igniting at that time–not earlier.
Now let’s compare the weekly homicide trends with social mobility data. Social mobility in the U.S. plummeted in mid-March as the pandemic struck, but then moved back to normal levels at a steady pace from early April through the late summer. Depicted below, for example, is national social mobility data from the last year from Apple, based on iPhone routing requests:
As readily apparent, from a nadir in early April, social mobility rebounded fairly smoothly through the summer of 2020. Given that the pandemic struck in mid-March and social mobility began returning normal levels in early April, the timing of the homicide spike does not appear to coincide with the pandemic. Indeed, the new Rosenfeld report acknowledges that homicide rates increased “significantly” in June, “well after the pandemic began, coinciding with the death of George Floyd and the mass protests that followed.”
Other analysis of national homicide trends confirms the conclusion that homicides (and shootings) were largely unaffected by the pandemic’s onset. For example, Professor David Abrams has published a detailed analysis of crime data from 25 large U.S. cities for January through May 2020. Abrams concluded that, as of the end of May, “[s]ome types of serious violent crime seemed unaffected by the pandemic onset, notably homicide and shootings.”
The Rosenfeld report (and the Abrams analysis just discussed) rely on aggregate data from a number of cities. But it is useful to drill down into particular cities to see if any patterns emerge. I have previously res
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