Step 1: More on How Aggregation Can Change Your Targeted Causal Effects: A Lesson from Counties, States, and Individuals

More on diff-in-diff checklist

I’m constantly thinking about the averaging of treatment effects. And when I say constantly, what I mean is “a lot”. I do so because I teach this material a lot and intend to go on tangents when I do. And this has been one of those. It’s like I’ll see this really obvious point while teaching something — like how an average treatment effect literally div…