A cartel is a formal (explicit) agreement among firms. Cartels usually occur in an oligopolistic industry, where there is a small number of sellers and usually involve homogeneous products. Cartel members may agree on such matters as price fixing, total industry output, market shares, allocation of customers, allocation of territories, bid rigging, establishment of common sales agencies, and the division of profits or combination of these. The aim of such collusion is to increase individual member's profits by reducing competition. Competition laws forbid cartels. Identifying and breaking up cartels is an important part of the competition policy in most countries, although proving the existence of a cartel is rarely easy, as firms are usually not so careless as to put agreements to collude on paper.
Several economic studies and legal decisions of antitrust authorities have found that the median price increase achieved by cartels in the last 200 years is around 25%. Private international cartels (those with participants from two or more nations) had an average price increase of 28%, whereas domestic cartels averaged 18%. Less than 10% of all cartels in the sample failed to raise market prices.