When every individual's effort imposes negative externalities, self-interested behavior leads to socially excessive effort. To curb these excesses when effort cannot be monitored, competing output-sharing partnerships can form. With the right-sized groups, aggregate effort falls to the socially...

Individuals extracting common-pool resources in the field sometimes form output-sharing groups to avoid costs of crowding. In theory, if the right number of groups forms, Nash equilibrium aggregate effort should fall to the socially optimal level. Whether individuals manage to form the efficient...