Market Structures
Compare perfect competition, monopolistic competition, oligopoly, monopoly, barriers to entry, price setting, and antitrust concerns.
A lesson of Economics, in Microeconomics, about 10 minutes.
By the end of this lesson, you will be able to describe the four main market structures, compare their characteristics and outcomes, and analyze how market power affects prices, output, and economic efficiency.
Why Market Structure Matters
Not all markets work the same way. A wheat farmer can sell at whatever price the market gives; a cable company can charge what it wants in your area. The structure of a market — how many sellers, how different their products are, how easy it is to enter — determines the power sellers have over prices and the efficiency of outcomes.
Perfect Competition
Characteristics:
- Many buyers and many sellers
- Identical (homogeneous) products
- Perfect information
- Free entry and exit
- Price takers: no single buyer or seller can affect market price
Examples: agricultural commodity markets (wheat, corn), some financial markets.
Short-run equilibrium: firms can earn profits or losses.
Long-run equilibrium: zero economic profit.
- If profits → new firms enter → supply increases → price falls → profits eroded
- If losses → firms exit → supply decreases → price rises → losses eliminated
Efficiency: perfectly competitive markets achieve allocative efficiency (P = MC) and productive efficiency (minimum average cost). Resources go to their highest-valued uses.
This is the benchmark: all other market structures are compared against perfect competition.
Monopoly
Characteristics:
- Single seller
- Unique product with no close substitutes
- High barriers to entry (legal monopoly, control of resource, natural monopoly)
- Price maker: chooses the price (or output)
Examples: utilities (regulated), De Beers (diamonds historically), Microsoft Windows in the 1990s.
Revenue relationships:
- Monopolist faces the entire downward-sloping market demand curve
- To sell more, must lower price for all units (marginal revenue < price)
Profit maximization: produce where $MR = MC$.
Comparison to perfect competition:
- Monopolist charges a higher price and produces less than the competitive outcome
- Deadweight loss: units worth more than their cost of production are not produced; economic inefficiency