Why Do Small Alcohol Tax/Price Hikes Have Such Large Effects On Drunk Driving Casualties?

We have noted before how alcohol tax (and thus price) hikes have been proven time and again to save lives, whether from traffic deaths, other accidental deaths, violent deaths, as well as deaths from more direct alcohol-related conditions such as alcoholic liver disease.  The question remains, why such relatively small differences in price have such relatively large effects, that can sometimes even be large enough to strain the reader's credulity?

For things like liver cirrhosis, the answer is pretty straightforward:  cirrhosis is chronic and cumulative, but it is also progressive as well.  At any given time, some unknown number of people (and unknown to the people themselves as well) may be just one binge away from near-certain death.  And for them, even a very modest near-term reduction in drinking due to a price hike (which to a very heavy drinker, is not trivial, since they spend so much on alcohol) can very well save their life.

But what about less direct things like drunk driving casualties?  Well, one needs to think like an economist, that is, on the margin.  It is the last drink of any given drinking session that determines one's final BAC of the session, and it is the final BAC that determines how impaired one is in the event of driving home.  And we know that the fatal or serious crash risk rises exponentially with BAC, thus even a modest reduction (say, one fewer drink per session) would dramatically reduce the risk of such casualties, even though the risk still remains significantly elevated compared to not drinking at all before driving.  At on-premise locations like bars, a tax hike is likely to be passed through at a rate greater than one-to-one due to rounding up, so it is very plausible that at least some people will have one fewer drink per session as a result.  Or alternatively, they may drink before going out to save money, but that would make them more likely to plan ahead and not drive there, so they would be even less likely to drive back home as a result. 

Either way, the fairly recent examples of Illinois and Maryland seeing sizeable reductions in traffic deaths after relatively modest alcohol tax hikes in 2009 and 2011, respectively, definitely supports this hypothesis.  And it shows that this classic "tax-price-consumption-fatalities" relationship is still as relevant as ever now in the 21st century, even if it has been attenuated a bit since the 1980s.  And most of the gazillion studies on the matter have found that the effect is larger than that of the meretricious "crown jewel" of the neo-prohibitionist public health fascists and ageist bigots, namely the 21 drinking age, with the supposed lifesaving effect of the latter being most likely spurious, inconsequential, or even perverse in the long run.

In other words, it's really a no-brainer to raise alcohol taxes, yesterday.  Especially with alcohol being so dangerously cheap right now in America.  So what are we waiting for?