How Does Lethality Increase Homicide Rates
In the District of Columbia, there is an interesting trend emerging. While the homicide rates have indeed been increasing, the level of violent crime has been decreasing…but how can that be?
Surely more violent crime would lead to more homicides, right? Not necessarily, and in DC, quite the opposite it seems! The reason for this is something called “lethality”.
People who get shot don’t always die. Many survivors of actual gun shot wounds live on, some uninterrupted by the tragedy that befell them. Of course, many instances occur in which people have physical ailments for the rest of their lives due to the wounds inflicted upon them. A bullet in the spine will likely leave a person paralyzed. A bullet in the brain may lead to brain damage. But without the victim dying, it is not a homicide, but a violent assault and attempted homicide instead.
If you divide the homicide rate by the total incident rate, you get a measure of the “lethality” of the incidents. That is, the probability that a gun related violent assault will lead to death. This metric has been unusually high in DC over the past year. The equation would look something like this:
Lethality = Homicides/Overall Assault with a dangerous weapon
= Homicides/(Homicides + Assault with a dangerous weapon)
Comparing the statistics from 2017 and 2018 we see an interesting change.
Table credit: DCMPD, https://mpdc.dc.gov/page/district-crime-data-glance
For 2017, the percentage of assaults that led to death was 116/(116+1861)*100% = 5.8%
For 2018, the percentage of assaults that led to death was 160/(160+1674)*100% = 8.7%
This jump helps explain the rise of homicides during a year that say a decrease in violent crime.
How can we account for this? Some of it is just blind luck. A bullet hits an artery instead of grazing the shoulder. A response time is a little longer and the person’s life is lost. As hard as it can be to maintain a positive image of everything going on, sometimes a brief reminder of other positive trends (like that of violent crime decreasing) can give us the fortitude to continue, knowing that we can in fact make a difference.