Here is an excellent post by Alec Stapp, easy to read but a bit hard to excerpt but here are the closing bits:
As a few others pointed out, these relatively small moves in AT&T and Verizon (less than 3 percent in either direction) may just be noise. That’s certainly possible given the magnitude of the changes. Contra Philippon, I think the methodology in question is too weak to rule out the pro-competitive theory of the case, i.e., that the new merged entity would be a stronger competitor to take on industry leaders AT&T and Verizon. We need much more robust and varied evidence before we call anything “bogus.” Of course, that means this event study is not sufficient to prove the pro-competitive theory of the case, either.
Olivier Blanchard, the former chief economist of the IMF, shared Philippon’s thread on Twitter and added this comment above: “The beauty of the argument. Simple hypothesis, simple test, clear conclusion.”
If only things were so simple.
Recommended. Addendum: Philippon comments.