There are no true examples of perfect competition, but agricultural products are often used as an example. Product differentiation, making buyers think similar products are different, is a key to success. Under monopolistic competition, individual sellers set prices. The fast food industry is an example. The initial investment is usually high.
Prices tend to be close to the same.
Examples include breakfast cereal, beer, automobiles, and soft drinks. In the U.S. laws prohibit the creation of monopolies, but do permit approved monopolies such as public utilities. New legislation is likely to result in fewer, larger utilities and lower prices. There are interferences to the free exchange of goods and services among countries. This results in surpluses in some countries and shortages in others.