Enterprise that provides certain classes of services to the public, including common-carrier transportation (buses, airlines, railroads); telephone and telegraph services; power, heat and light; and community facilities for water and sanitation. In most countries such enterprises are state-owned and state-operated; in the U.S. they are mainly privately owned, but they operate under close regulation. Given the technology of production and distribution, they are considered natural monopolies, since the capital costs for such enterprises are large and the existence of competing or parallel systems would be inordinately expensive and wasteful. Government regulation in the U.S., particularly at the state level, aims to ensure safe operation, reasonable rates, and service on equal terms to all customers. Some states have experimented with deregulation of electricity and natural-gas operations to stimulate price reductions and improved service through competition, but the results have not been universally promising.