We re-examine tacit collusion under a simple punishment rule in which firms match any lower price by their rivals, but otherwise leave their prices unchanged. We provide conditions under which this simple rule sustains collusion and is credible. Provided competition is imperfect, collusion can...

In merger analysis and other antitrust settings, risk is often cited as a potential barrier to entry. But there is little consensus as to the kinds of risk that matter- systematic versus non-systematic and industry-wide versus firm-specific - and the mechanisms through which they affect entry. I...