Opposition to anticompetitive coordination once animated merger policy. But after consecutive decades of decline, evidence now suggests that coordinated effects cases are disfavored among enforcers and are rarely pursued. This change in merger enforcement is dangerous and puzzling. Coordinated...

Antitrust analysis is famously complex, fact intensive, and time consuming. But should we aspire for it to be otherwise? I offer two cautionary conjectures in opposition to the search for simpler rules. First, I conjecture that efforts to convert vague antitrust standards into clear rules will...

We provide evidence on the least biased ways to identify causal effects in situations where there are multiple outcomes that all depend on the same endogenous regressor and a reasonable but potentially contaminated instrumental variable that is available. Simulations provide suggestive evidence...