Measuring Luck in NOLA Gun Violence in November

A lot of things can happen when a bullet leaves a gun and my general contention for a while has been that the final outcome of whether a person is hit and whether that shooting is fatal or non-fatal is often random. Given enough incidents over time the randomness will tend to even out, but there can be great variations from day to day and from month to month. Measuring these variations using firearm discharge reports can help determine when New Orleans has gotten “lucky” and “unlucky” which might suggest when our luck will flip.

Firearm discharge report data is available through Calls for Service since September 2013. It actually goes back earlier but I prefer to use incidents where the initial signal was of a discharging firearm (NOPD’s Calls for Service system was upgraded in September 2013 hence the cut off date).

There have been just over 14,000 firearm discharge reports, 1,800 shooting incidents and 640 fatal shooting victims over that span. That works out to 7.7 firearm discharge reports per shooting incident and 22.1 per fatal shooting victims on average. Luck, therefore, could be defined as the number of shooting incidents or fatal shooting victims above or below what would be expected under average conditions.

There have been 27 shooting incidents and 14 people shot to death so far in November 2017, but measuring the city’s luck suggests roughly average luck regarding the number of fatal shooting victims (given this month’s level of firearm discharge reports) with very good luck in terms of the number of shooting incidents. The amount of luck per month can be seen back to January 2014 in the below table.

So far in 2017 there have been 10 fewer shooting incidents and 20 fewer fatal shooting victims than average luck would suggest. In 2016, by contrast, there were 14 more shooting incidents and 1 fewer fatal shooting victim than average.

The below chart shows how these things tend to even out over time.

In other words, shootings may have slowed down in New Orleans in November but gun violence has not.