Why Monopolies Arise? Monopoly is a rm that is the sole seller of a product without close substitutes. The fundamental cause of monopoly is barriers to entry: A monopoly remains the only seller in its market because other rms cannot enter the market and compete with it. Barriers to entry have three main sources: 1. Monopoly Resources. A key resource is owned by a single rm. Example: The DeBeers Diamond Monopoly|this rm controls about 80 percent of the diamonds in the world. 2. Government-Created Monopolies. Monopolies can arise because the government grants one person or one rm the exclusive right to sell some good or service. Patents are issued by the government to give rms the exclusive right to produce a product for 20 years. 3. Natural Monopoly: a monopoly that arises because a single rm can supply a good or service to an entire market at a smaller cost than could two or more rms. A natural monopoly occurs when there are economies of scale, implying that average total cost falls as the rm's scale becomes larger.
Monopoly versus Competition The key di erence between a competitive rm and a monopoly is the monopoly's ability to control price. The demand curves that each of these types of rms faces is di erent as well. 1. A competitive rm faces a perfectly elastic demand at the market price. The rm can sell all that it wants to at this price. 2. A monopoly faces the market demand curve because it is the only seller in the market. If a monopoly wants to sell more output, it must lower the price of its product. A monopoly's marginal revenue will always be less than the price of the good (other than at the rst unit sold). 1. If the monopolist sells one more unit, his total revenue (P Q) will rise because Q is getting larger. This is called the output e ect. 2. If the monopolist sells one more unit, he must lower price. This means that his total revenue (P Q) will fall because P is getting smaller. This is called the price e ect. Remember that demand