When firms compete in the managerial labor market, the choice of corporate governance by a firm affects, and is affected by, the choice of governance by other firms. Firms with weaker governance offer managers more generous incentive compensation, which induces firms with good governance to also overpay their management. Due to this externality, overall level of governance in the economy can be inefficiently low. Poor governance can in fact be employed by incumbent firms to deter entry by new firms. Such corporate governance externalities have important implications for regulatory standards, ownership structure of firms, and the market for corporate control.

Prior theoretical research has found that, in the absence of regulation, a greater number of insiders leads to more insider trading. We show that optimal regulation features detection and punishment policies that become stricter as the number of insiders increases, reducing insider trading in equilibrium. We construct measures of the likelihood of insider activity prior to bid announcements of private-equity buyouts during the period 2000–2006 and relate these to the number of financing participants. Suspicious stock and options activity is associated with more equity participants, while suspicious bond and CDS activity is associated with more debt participants — consistent with models of limited competition among insiders but inconsistent with our model of optimal regulation.