600 International Organization reward for collective action in OPEC's case,so one might expect deep cooperation. Popular wisdom also holds that OPEC is influential,but economic studies investi- gating OPEC's market impact have had difficulty finding conclusive evidence. This generates two questions.First,does OPEC operate as a cartel,meaning that it significantly restricts its members'oil production in order to affect prices?Second, if OPEC is not actually a cartel,why do so many people believe that it is? The first step is to investigate whether OPEC actually acts as a cartel.5 Using some of the same tests that in the past have helped evaluate the impact of the WTO and other organizations,I find that OPEC rarely if ever constrains or influences the oil production rate of its member states.Although this article is not the first to question OPEC's effec- tiveness in restricting the oil supply,6 there is sufficient debate and ambiguity in the existing literature to sustain OPEC's image,even among scholars,as a cartel that manipulates the price of oil by restricting supply.Therefore,I conduct four empirical tests in search of OPEC's effect on oil production,at least two of which are entirely novel.I find that OPEC membership is not significantly correlated with lower oil pro- duction once other relevant factors are controlled for.At a minimum,there is no good evidence to believe that OPEC is a cartel,and I shift the burden of proof to those who would claim that OPEC facilitates economic collusion.I make no claim about whether OPEC could restrict oil supply in principle;I simply argue that it does not do so in prac- tice.This is due in part,but not principally,to endemic cheating by OPEC members (that is,oil production in excess of their quotas).A cartel needs to set tough goals and meet them;OPEC sets easy goals and fails to meet even those. There was one occasion on which OPEC did have a significant impact on the world oil market,namely the 1973 oil crisis,but OPEC's role in the crisis has been greatly misunderstood.That event helped to endow OPEC with a reputation as a manipulator of world oil markets. If OPEC does not operate as a cartel,why do so many people believe that it does? The idea of OPEC as a cartel is a"rational myth"that supports the organization's true principal function,which is to generate political benefits for its members.Scholars have found that various organizations adopt rational myths,?and OPEC would not be the first international institution to outlive its original mandate.8 OPEC's current role is obscured in part by the complexity of the world oil market,in part by the fact that one of its members,Saudi Arabia,probably does have some market power on its own (distinct from the organization to which it belongs),and in part by misdirection by OPEC itself.OPEC's perceived market power is a useful fiction that generates pol- itical benefits for its members with domestic and interational audiences. 5.A cartel is defined as a group of firms(or states,in this case)that creates agreements about quantities to produce or prices to charge.Mankiw 2011,351.More details later. 6.As I show,the debate thus far has been principally among economists;the paucity of attention given to OPEC noted earlier describes political science.This disciplinary divergence has consequences:economic analyses of OPEC typically omit important political variables,potentially biasing the results. 7.See McNamara 2002;Boiral 2007;and Meyer and Rowan 1977. 8.See Bamett and Finnemore 1999:Gray 2011:Duffield 1994:and Wallander 2000.reward for collective action in OPEC’s case, so one might expect deep cooperation. Popular wisdom also holds that OPEC is influential, but economic studies investi￾gating OPEC’s market impact have had difficulty finding conclusive evidence. This generates two questions. First, does OPEC operate as a cartel, meaning that it significantly restricts its members’ oil production in order to affect prices? Second, if OPEC is not actually a cartel, why do so many people believe that it is? The first step is to investigate whether OPEC actually acts as a cartel.5 Using some of the same tests that in the past have helped evaluate the impact of the WTO and other organizations, I find that OPEC rarely if ever constrains or influences the oil production rate of its member states. Although this article is not the first to question OPEC’s effec￾tiveness in restricting the oil supply,6 there is sufficient debate and ambiguity in the existing literature to sustain OPEC’s image, even among scholars, as a cartel that manipulates the price of oil by restricting supply. Therefore, I conduct four empirical tests in search of OPEC’s effect on oil production, at least two of which are entirely novel. I find that OPEC membership is not significantly correlated with lower oil pro￾duction once other relevant factors are controlled for. At a minimum, there is no good evidence to believe that OPEC is a cartel, and I shift the burden of proof to those who would claim that OPEC facilitates economic collusion. I make no claim about whether OPEC could restrict oil supply in principle; I simply argue that it does not do so in prac￾tice. This is due in part, but not principally, to endemic cheating by OPEC members (that is, oil production in excess of their quotas). A cartel needs to set tough goals and meet them; OPEC sets easy goals and fails to meet even those. There was one occasion on which OPEC did have a significant impact on the world oil market, namely the 1973 oil crisis, but OPEC’s role in the crisis has been greatly misunderstood. That event helped to endow OPEC with a reputation as a manipulator of world oil markets. If OPEC does not operate as a cartel, why do so many people believe that it does? The idea of OPEC as a cartel is a “rational myth” that supports the organization’s true principal function, which is to generate political benefits for its members. Scholars have found that various organizations adopt rational myths,7 and OPEC would not be the first international institution to outlive its original mandate.8 OPEC’s current role is obscured in part by the complexity of the world oil market, in part by the fact that one of its members, Saudi Arabia, probably does have some market power on its own (distinct from the organization to which it belongs), and in part by misdirection by OPEC itself. OPEC’s perceived market power is a useful fiction that generates pol￾itical benefits for its members with domestic and international audiences. 5. A cartel is defined as a group of firms (or states, in this case) that creates agreements about quantities to produce or prices to charge. Mankiw 2011, 351. More details later. 6. As I show, the debate thus far has been principally among economists; the paucity of attention given to OPEC noted earlier describes political science. This disciplinary divergence has consequences: economic analyses of OPEC typically omit important political variables, potentially biasing the results. 7. See McNamara 2002; Boiral 2007; and Meyer and Rowan 1977. 8. See Barnett and Finnemore 1999; Gray 2011; Duffield 1994; and Wallander 2000. 600 International Organization