A market is one of the many varieties of systems, institutions, procedures, social relations and infrastructures whereby parties engage in exchange. While parties may exchange goods and services by barter, most markets rely on sellers offering their goods or services (including labor) in exchange for money from buyers. It can be said that a market is the process by which the prices of goods and services are established. Markets facilitate trade and enables the distribution and allocation of resources in a society. Markets allow any trade-able item to be evaluated and priced. A market emerges more or less spontaneously or may be constructed deliberately by human interaction in order to enable the exchange of rights (cf. ownership) of services and goods. Markets can differ by products (goods, services) or factors (labour and capital) sold, product differentiation, place in which exchanges are carried, buyers targeted, duration, selling process, government regulation, taxes, subsidies, minimum wages, price ceilings, legality of exchange, liquidity, intensity of speculation, size, concentration, information asymmetry, relative prices, volatility and geographic extension. The geographic boundaries of a market may vary considerably, for example the food market in a single building, the real estate market in a local city, the consumer market in an entire country, or the economy of an international trade bloc where the same rules apply throughout. Markets can also be worldwide, for example the global diamond trade. National economies can be classified, for example as developed markets or developing markets. In mainstream economics, the concept of a market is any structure that allows buyers and sellers to exchange any type of goods, services and information. The exchange of goods or services, with or without money, is a transaction. Market participants consist of all the buyers and sellers of a good who influence its price, which is a major topic of study of economics and has given rise to several theories and models concerning the basic market forces of supply and demand. A major topic of debate is how much a given market can be considered to be a “free market”, that is free from government intervention. Microeconomics traditionally focuses on the study of market structure and the efficiency of market equilibrium, when the latter (if it exists) is not efficient, then economists say that a market failure has occurred. However it is not always clear how the allocation of resources can be improved since there is always the possibility of government failure.