Sources of monopoly power A monopoly, unlike a perfectly competitive firm, has some market power. Thus, it can raise its price, within limits, without quantity demanded falling to zero. The main way monopolies retain their market power is through barriers to entry, which prevent other companies from entering monopolized markets and competing for customers.
Consider the market for tanzanite. The mines for this blue-purple gemstone, found only in Tanzania, are owned by the local government. Given that no one is allowed into the mines without government permission, the market structure for tanzanite highly resembles that of a monopoly.
Which of the following best explains the barriers to entry that exist in this scenario?

a) Control of a scarce resource
b) Legal restrictions
c) Economies of scale