There are four major market structures; perfect competition, monopolistic competition, oligopoly and monopoly. Perfect competition is a market structure in which there are many sellers and buyers, firms produce a homogeneous product, and there is free entry and exit from the industry (Amacher & Pate, 2013). Perfect competition is characterized by the fact that homogeneous products are created. In this case, consumers do not tend to buy one product over another because they are all the same. Perfect competitions are also set up so that firms are free to enter and exit a market as they please. They are allowed to act without any restrictions, whether from the government or other companies. This structure is purely theoretical and represents the extreme end of market structure. The opposite end of the market structure to perfect competition is monopoly. Monopolies arise when there is only one supplier of a specific good, who has no alternatives. Monopolies can be natural or artificial. Some of the natural monopolies a city will see are businesses such as utilities or, for cities like Clarksville that only have one, hospitals. With only one hospital and no other within a two-hour drive, Clarksville Hospital has a monopoly on emergency care, as there are no other options for this type of service in the region. Artificial monopolies are created by various means, including allowing others to enter the market. Artificial monopolies are generally rare, if any, due to antitrust laws designed to prevent this in legitimate businesses. However, even though these two are the extreme ends of the spectrum, the majority of companies will find themselves in the middle of paper with higher barriers, all trying to compete for those profits. (2010). Retrieved from http://www.census.gov/Amacher, R. and Pate, J. (2013). Principles and policies of microeconomics. San Diego, CA: Bridgepoint Education, Inc. Orr, D. (1974). An index of entry barriers and its application to the market performance-structure relationship. Journal of Industrial Economics, 23(1), 11-39. Retrieved from http://eds.a.ebscohost.com.proxy-library.ashford.edu/eds/detail?sid=25f46629-86ce-4fba-b338-6ba319c80f42@sessionmgr4004&vid=1&hid=4210&bdata=JnNpdGU9ZWRzLW xpdmU=Schaefer, S . (2013). Detroit files largest municipal bankruptcy on record. Forbes Magazine, retrieved from http://eds.b.ebscohost.com.proxy-library.ashford.edu/eds/detail? vid=2&sid=b6189574-03df-4c57-b7ad-a175dc56aebf@sessionmgr113&hid=102 &bdata=JnNpdGU9ZWRzLWxpdmU=