Last updated on August 17, 2019
Earlier this year I wrote two posts about Judea Pearl’s front-door criterion, and how to use it in a regression context (see here and here).
After writing those posts and seeing a few Twitter exchanges on the topic, I realized that a formal guide explaining how to use the front-door criterion in practice might be useful, and discussed with my PhD student Jeff Bloem–who is on the market this year; check out his CV here and consider hiring him–the possibility of working on such a paper together.
In this new working paper titled “The Paper of How”—an obvious play on dad joke about the title of Judea Pearl’s The Book of Why—we present just such a guide. More interestingly, however, we also (i) present three empirical illustrations of the front-door criterion, and (ii) explore what happens when the assumptions underlying the front-door criterion fail to hold.
Here is the abstract of this new paper, on which we welcome your comments:
Empirical social science nowadays consists largely of attempts at answering questions of the form “Does X cause Y?” As a result, social scientists rely on a number of empirical techniques aimed at disentangling causal relationships from mere correlations. One such technique is Judea Pearl’s (1995, 2000) front-door criterion, which relies for identification on the presence of a single, strictly exogenous mechanism on the causal path between the treatment and outcome. Social scientists in general–and economists in particular–have been resistant to the idea of adding the front-door criterion to the standard empirical toolkit, largely due to the difficulty posed by finding the required mechanism. To help overcome that resistance, we first explain how to use the front-door criterion in a regression context. We then present three empirical illustrations of the front-door criterion. Finally, and most importantly, we look at what happens when some of the assumptions underpinning the front-door criterion are violated.