So. A reporter asked me what I thought of this article, “Providing driver’s licenses to unauthorized immigrants in California improves traffic safety,” by Hans Lueders, Jens Hainmueller, and Duncan Lawrence. It’s embargoed! so I’m not supposed to post anything on it until now.
From the abstract:
We examine the short-term effects of . . . California’s Assembly Bill 60 (AB60), under which more than 600,000 [driver’s] licenses were issued in the first year of implementation in 2015 . . . We find that, contrary to concerns voiced by opponents of the law, AB60 has had no discernible short-term effect on the number of accidents. The law primarily allowed existing unlicensed drivers to legalize their driving. We also find that, although AB60 had no effect on the rate of fatal accidents, it did decrease the rate of hit and run accidents, suggesting that the policy reduced fears of deportation and vehicle impoundment. . . .
The paper seems reasonable to me.
But I’d like to see what would happen if they would perform the same analysis but using 2014 as their break point, or 2013, or 2011, or 2010, etc. They’re looking at changes in 2015 that are correlated with %AB60 licences, but (a) other things can be happening in 2015, and (b) there are lots of things correlated with this county predictor. Also, the %AB60 licenses is low (always less than 6%, so it seems from the graphs). It would seem to me that lots of things can be driving the rate of collisions and the rate of hit and runs. So the causal story does not seem so clear to me. There are too many alternative explanations.
So, I’m with them when they say that the data show no evidence of negative consequence from the law allowing driver’s licenses for unauthorized immigrants. But I’d need more evidence to be convinced of their causal claims, in particular on the hit and runs. That seems like more of a reach.
To put it another way, the paper is called, “Providing driver’s licenses to unauthorized immigrants in California improves traffic safety,” but I’d be happier with a title such as “No evidence that providing driver’s licenses to unauthorized immigrants in California decreases traffic safety.”
P.S. The paper is in PPNAS but the editor is not Susan Fiske so I guess I should really just call it PNAS this time.