2. Discuss the welfare effects of monopolies and oligopolies.
3. Which actions you think OPEC will take over the next year?
In economics, a monopoly (from the Greek monos, one + polein, to sell) is defined as a persistent market situation where there is only one provider of a kind of product or service. Monopolies are characterized by a lack of economic competition for the good or service that they provide and a lack of viable substitute goods.
Monopoly should be distinguished from monopsony, in which there is only one buyer of the product or service; it should also, strictly, be distinguished from the (similar) phenomenon of a cartel. In a monopoly a single firm is the sole provider of a product or service; in a cartel a centralized institution is set up to partially coordinate the actions of several independent providers (which is a form of oligopoly).
A monopoly based on laws explicitly preventing competition is a legal monopoly or de jure monopoly. When such a monopoly is granted to a private party, it is a government-granted monopoly; when it is operated by government itself, it is a government monopoly or state monopoly. A government monopoly may exist at different levels of government (eg just for one region or locality); a state monopoly is specifically operated by a national government.
An example of a "de jure" monopoly is AT&T, which was granted monopoly power by the US government, only to be broken up in 1982 following a Sherman Antitrust suit.
An oligopoly is market form in which a market is ...