Advocates of free enterprise argue that a decentralized MARKET-based system leads to a more efficient allocation of productive resources in line with the demands of buyers and that in pursuit of individual self-interest (the profit motive) it will produce economic results (lower costs and prices, innovative new products) that are beneficial to society as a whole. Critics of private-enterprise economies argue, however, that market-based economies may not fully respond to the demands of buyers where supply is in the hands of powerful suppliers (see MONOPOLY), that it cannot ensure the provision of COLLECTIVE PRODUCTS for which no market exists, that it can generate POLLUTION and other EXTERNALITIES and that it leads to gross inequalities in INCOME DISTRIBUTION. (See PRICE SYSTEM.) See CENTRALLY PLANNED ECONOMY, MIXED ECONOMY, NATIONALIZATION, PRIVATIZATION, LAISSEZ-FAIRE.