Looking back it should have been obvious. In my previous post about the falling automobile fatality rate I hinted it might be due to recessions and/or advances in car technology and their introduction rate to the road. The answer turned out to be much simpler.
From 1979-2010 the number of automobile related fatalities fell from 51,093/year to 32,708. In 1982 the National Highway Traffic Safety Administration started tracking which of these deaths were alcohol related. In 1982 the percentage was 59.6%, but by 2008 it had fallen to 37.2%.
Automobile Deaths 1982-2008
From 1982-2008, not only did all the gains in highway safety come from a reduction in alcohol related deaths, they even offset an increase in non-alcohol related deaths.
Change in Automobile Deaths 1982-2008
To avoid confusion, positive values in this chart are always “good” (ie. unemployment rate going down is green, death rate going up is red, etc).
In retrospect this seems like an obvious answer, but during my search for the cause of the trend I checked against population change, total miles driven, recessions, unemployment, and other factors. The thing that lead me to track alcohol vs non-alcohol related fatalities was that I found a strong correlation between a drop in deaths and higher unemployment, but a weak correlation between fewer deaths and fewer miles driven. Also, the fatality rate didn’t spike back up once unemployment started to go back down. There’s a strong correlation between spikes in unemployment and non-alcohol related fatalities, but you can see the fatality rate return once employment comes back. It’s not shown in the chart above, but strangely we don’t see a large decrease in the miles driven per person when unemployment is high. I can only guess that having free time during the day leads to more opportunities to drive that are for, whatever reason, less likely to result in a fatal accident.
Alcohol related deaths, however, see fluctuating but continuous improvement with one notable exception, 1984-1985 when the number of deaths increased by 1,850 (7.4%) from the previous year. I’m not sure what happened there.
Now that we know the primary cause of the reduction in deaths, the question becomes how did we do it? My guess is a consistent anti-drinking and driving media campaign resulting in fewer drunk drivers on the road? Governments and manufacturers have put a lot of effort into making cars safer, but it doesn’t appear to have had much of an effect over the last 30 years. Future improvements in the fatality rate will be harder and harder to come by.
Sources: Alcoholalert.com, Census.gov, FARS-NHTSA, Wikipedia, BLS.gov