Does regression discontinuity (or, more generally, causal identification + statistical significance) make you gullible?

Yes basically. This one’s pretty much a perfect example of overfitting, finding a discontinuity out of noise, in that if you just draw a smooth line through each graph, it actually looks better than the discontinuous version. We see this a lot: There’s no discontinuity in the data, but it’s possible to make a discontinuity …