In a free Market both parties undertake the exchange because each expects to gain from it. Also, each will repeat the exchange next time or refuse to because his expectation has proved correct or incorrec in the recent past. Trade, or exchange, is engaged in precisely because both parties benefit; if they did not expect to gain, they would not agree to the exchange.
This simple reasoning refutes the argument against free trade typical of the mercantilist period of sixteenth- to eighteenth-century Europe and classically expounded by the famed sixteenth-century French essayist Montaigne. The mercantilists argued that in any trade, one party can benefit only at the expense of the other that in everl.y transaction there is a winner and a loser, an “exploiter” and an “exploited.” We can immediately see the problem in this still-popular viewpoint the willingness and even eagerness to trade means that both parties benefit. In modern game-theory jargon, trade is a win-win situation, a “positive-sum” rather than a “zero-sum” or “negative-sum” game.
How can both parties benefit from an exchange? Each one values the two goods or services differently, and these differences set the scene for an exchange. I, for example, am walking along with money in my pocket but no newspaper; the newsdealer, on the other hand, has plenty of newspapers but is anxious to acquire money. And so, finding each other, we strike a dea.

There are limits to free enterprise, however. Americans have always believed that some services are better performed by public rather than private enterprise. For instance, in the United States, government is primarily responsible for the administration of justice, education (although there are many private schools and training centers), the road system, social statistical reporting, and national defense. In addition, government often is asked to intervene in the economy to correct situations in which the price system does not work. It regulates "natural monopolies," for example, and it uses antitrust laws to control or break up other business combinations that become so powerful that they can surmount market forces. Government also addresses issues beyond the reach of market forces. It provides welfare and unemployment benefits to people who cannot support themselves, either because they encounter problems in their personal lives or lose their jobs as a result of economic upheaval; it pays much of the cost of medical care for the aged and those who live in poverty; it regulates private industry to limit air and water pollution; it provides low-cost loans to people who suffer losses as a result of natural disasters; and it has played the leading role in the exploration of space, which is too expensive for any private enterprise to handle.
In this mixed economy, individuals can help guide the economy not only through the choices they make as consumers but through the votes they cast for officials who shape economic policy. In recent years, consumers have voiced concerns about product safety, environmental threats posed by certain industrial practices, and potential health risks citizens may face; government has responded by creating agencies to protect consumer interests and promote the general public welfare.
The U.S. economy has changed in other ways as well. The population and the labor force have shifted dramatically away from farms to cities, from fields to factories, and, above all, to service industries. In today's economy, the providers of personal and public services far outnumber producers of