OPEC has long been Saudi Arabia reducing output, and everyone else selling everything they can. They haven't had much power since the 1970s, but that they exist means they are a threat that if everyone else actually stuck to the agreement for a change.
This is the common problem for cartels: everyone has inventive to cheat on the deals made. By selling a little more than your share you get more money, while because everyone else is following along the prices are higher. (see also prisoners dilemma)
This is the common problem for cartels: everyone has inventive to cheat on the deals made. By selling a little more than your share you get more money, while because everyone else is following along the prices are higher. (see also prisoners dilemma)