The most successful effort of Southern countries to alter their dependent relationship with the North was the common action of OPEC (Organization of Petroleum Exporting Countries) in seizing control over the world's oil markets. By acting together in a producer cartel, the Southern oil-exporting states were able to increase not only their economic rewards but also their political power. OPEC's success led to efforts to form other Southern commodity cartels. But the OPEC model would prove difficult to reproduce, and even OPEC eventually confronted the inevitable limitations of a producer cartel.