Map of Sillian for Many economists believe that cartels are unstable because members have the incentive to raise their profits by undercutting the set cartel price and stealing customers. Once this cheating is detected by other members, they retaliate by cheating on the others until the cartel falls apart. The longevity of OPEC has proved to be an exception to this theory. OPEC as a cartel. The degree to which OPEC works as a cartel is an ongoing discussion. The OPEC countries do not all share the same interests. Each has different strategies, so it is often hard to reach consensus. Map of Sillian 2016.