In economics, a cartel is an agreement between competing firms to control prices or exclude entry of a new competitor in a market. It is a formal organization of sellers or buyers that agree to fix selling prices, purchase prices, or reduce production using a variety of tactics. Cartels usually arise in an oligopolistic industry, where the number of sellers is small or sales are highly concentrated and the products being traded are usually commodities. Cartel members may agree on such matters as setting minimum or target prices (price fixing), reducing total industry output, fixing market shares, allocating customers, allocating territories, bid rigging, establishment of common sales agencies, altering the conditions of sale, or combination of these. The aim of such collusion (also called the cartel agreement) is to increase individual members' profits by reducing competition. If the cartelists do not agree on market shares, they must have a plan to share the extra monopoly profits generated by the cartel.One can distinguish private cartels from public cartels. In the public cartel a government is involved to enforce the cartel agreement, and the government's sovereignty shields such cartels from legal actions. Inversely, private cartels are subject to legal liability under the antitrust laws now found in nearly every nation of the world. Furthermore, the purpose of private cartels is to benefit only those individuals who constitute it, public cartels, in theory, work to pass on benefits to the populace as a whole.Competition laws often forbid private 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 collusion agreements 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%. Fewer than 10% of all cartels in the sample failed to raise market prices.[citation needed]