US drinking age and road deaths

Thomas Lumley at Stats Chat blogs:

In an earlier post I looked at male youth suicide rates in the US before and after the drinking age was raised in July 1984, and said that expecting a decrease in road deaths made sense.  It does make sense, but it seems that it didn’t happen in the US.  …

The graph shows road deaths per 100,000 people by age group (from CDC), and there isn’t anything prominent that happens in 1984 or 1985.  The pattern is pretty much the same for ages 15-19, 20-24, and 25-34.  The younger two groups would have been affected by the law (with its supporters usually arguing that the youngest of the groups is the real target) and the oldest group would not have been affected.    You can think of all sorts of explanations for why a difference might not have been seen (for example, the US is bad at detecting and deterring drunk drivers), but the data has to be disappointing to people who want a change in the drinking age.

The move in New Zealand to go to a split age may, in my view, increase the road toll. Why? Well 18 and 19 year olds will no longer be legally able to purchase some alcohol at an off-licence and take it home to drink. They will be forced to head out to bars to drink.

Now in Wellington this might not lead to an increase in drink driving, as it is such a compact city. But in Auckland it could well do so, and in more rural areas, I think is highly likely to. A split age will send out some bad incentives.