In this paper, I offer two ways in which firms can collude: secret monitoring and infrequent coordination. Such collusion is enforceable with intuitive communication protocols. I make my case in the context of a repeated Cournot oligopoly with flexible production, prices that follow a Brownian motion and no monetary side payments, an environment where it has previously been argued that any collusion is impossible. Trade associations can easily facilitate collusion by mediating communication amongst firms.

Suppose that providing incentives for a group of individuals in a strategic context requires a monitor to detect their deviations. What about the monitor's deviations? To address this question, I propose a contract that makes the monitor responsible for monitoring, and thereby provides incentives even when the monitor's observations are not only private, but costly, too. I also characterize exactly when such a contract can provide monitors with the right incentives to perform. In doing so, I emphasize virtual enforcement and suggest its implications for the theory of repeated games.