A challenge for many cartels is avoiding a destabilizing increase in non-cartel supply in response to having raised price. In the case of the German cement cartel that operated over 1991-2002, the primary source of non-cartel supply was imports from Eastern European cement manufacturers....

A manufacturer contracting secretly with several downstream competitors faces an opportunism problem, preventing it from exerting its market power. In an infinitely repeated game, the opportunism problem can be relaxed. We show that the upstream firm's market power can be restored even further...