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# Mass Shooting Casualties through 28 October

Summary:
Regression 1982q4-2018q3: f = -18.52 + 0.028pop + 5.182trump Adj.R2 = 0.18, N = 144, DW = 2.07, bold denotes significance at 10% msl using HAC robust standard errors. Where f denotes mass shooting fatalities, pop is population in millions, trump is a dummy variable for Trump administration. One can interpret this as follows: a Trump administration quarter is associated with 5.2 greater fatalities from mass shootings, or 20.8 on an annualized basis. (Over 1982q4-16q4, the average frequency per quarter is 4.876). Inclusion of a deterministic time trend yields a negative coefficient on population, and a trump coefficient (4.093) significant at 11% msl. Figure 1: Cumulative mass shooting fatalities (dark red), non-fatal injured (pink), from 1982M08. Orange denotes 2017M01-2018M10, light

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Regression 1982q4-2018q3:

f = -18.52 + 0.028pop + 5.182trump

Adj.R2 = 0.18, N = 144, DW = 2.07, bold denotes significance at 10% msl using HAC robust standard errors.

Where f denotes mass shooting fatalities, pop is population in millions, trump is a dummy variable for Trump administration.

One can interpret this as follows: a Trump administration quarter is associated with 5.2 greater fatalities from mass shootings, or 20.8 on an annualized basis. (Over 1982q4-16q4, the average frequency per quarter is 4.876). Inclusion of a deterministic time trend yields a negative coefficient on population, and a trump coefficient (4.093) significant at 11% msl.

Figure 1: Cumulative mass shooting fatalities (dark red), non-fatal injured (pink), from 1982M08. Orange denotes 2017M01-2018M10, light orange 2016M11-2017M01. Source: Mother Jones, accessed 10/28/2018, and author’s calculations.

The corresponding regression for mass shooting wounded:

w = -13.84 + 0.022pop + 26.815trump

Adj.R2 = 0.13, N = 144, DW = 2.36, bold denotes significance at 10% msl using HAC robust standard errors.

Where w denotes mass shooting wounded. This can be interpreted as 26.8 greater mass shooting wounded per quarter of Trump administration, or about 107.2 on an annualized basis. (Over 1982q4-16q4, the average frequency per quarter is 4.672). The results are robust to the inclusion of a time trend.

Now consider a count variable, and a Poisson regression:

Figure 2: Mass shooting count, from 1982M08. Orange denotes 2017M01-2018M10, light orange 2016M11-2017M01. Source: Mother Jones, accessed 10/28/2018, and author’s calculations.

events = -5.98 + 0.006pop + 0.267trump

Adj.R2 = 0.36, N = 144, DW = 2.36, bold denotes significance at 10% msl.

Where events denotes mass shooting event count. This means there are 0.267 more events per quarter of the Trump administration, or slightly more than one more per year on an annualized basis. (Over 1982q4-16q4, the average frequency per quarter is 0.577). The results are robust to inclusion of a time trend.

Correlation is not the same as causation — but causality is a very hard thing to identify. Granger causality suggests a less rigorous approach. One interesting fact is that the Charlottesville riot, and the president’s remarks about “good people on both sides”, precedes an intensification of mass shootings.

Figure 3: Mass shooting fatalities (dark red), from 2000M01. Orange denotes 2017M01-2018M10, light orange 2016M11-2017M01. Dark orange line at 2017M08. Source: Mother Jones, accessed 10/28/2018, and author’s calculations.

Figure 4: Mass shooting count, from 2000M01. Orange denotes 2017M01-2018M10, light orange 2016M11-2017M01. Dark orange line at 2017M08. Source: Mother Jones, accessed 10/28/2018, and author’s calculations.

He is Professor of Public Affairs and Economics at the University of Wisconsin, Madison