Perfectly Competitive Markets: Efficiency and Welfare
Perfectly Competitive Markets and Efficiency
A perfectly competitive market is considered the most efficient because it maximizes social surplus. Efficiency, in this context, is defined by the maximization of total well-being in society.
Five Assumptions of Perfect Competition
For a market to be perfectly competitive, it must meet five criteria:
- Atomicity
- Homogeneity
- Free entry and exit
- Perfect information
- Perfect mobility of production factors
The First Welfare Theorem
This theorem concludes that a perfectly competitive market is efficient based on three propositions:
- Goods are allocated to buyers who value them the most (highest reservation price).
- Production is allocated to the most efficient producers (lowest production costs).
- The market produces the exact quantity that maximizes social surplus.
Understanding Surpluses
Social surplus (SS) is the sum of consumer surplus (CS) and producer surplus (PS).
Consumer Surplus (CS)
The difference between the reservation price (maximum price a consumer is willing to pay) and the actual market price.
CS = Reservation Price – Market Price
Graphically, CS is the area between the demand curve and the market price.
Producer Surplus (PS)
The difference between the market price and the minimum price a firm is willing to accept (its production cost).
PS = Revenues – Costs
Graphically, PS is the area between the supply curve and the market price.
Social Surplus (SS)
SS = CS + PS. An efficient allocation maximizes this total, even if it does not maximize CS or PS individually.
Public Intervention and Price Controls
The state may intervene in a competitive market for reasons of social justice or market failure. However, any intervention that moves the market away from its equilibrium leads to a deadweight loss—a net loss of social welfare.
1. Ceiling Price (Maximum Price)
A policy that prevents the market price from rising above a certain level (e.g., rent control or bread prices).
- Effective Ceiling Price: Must be set below the equilibrium price.
- Consequences: Decrease in market price; increase in quantity demanded (D) and decrease in quantity supplied (S).
This leads to a shortage, where the new equilibrium quantity is limited to what companies are willing to produce at that low price (Q* = QS).
2. Floor Price (Minimum Price)
A policy that prevents the market price from falling below a certain level (e.g., minimum wage).
- Effective Floor Price: Must be set above the equilibrium price.
- Consequences: Increase in market price; decrease in quantity demanded and increase in quantity supplied.
This leads to overproduction or a surplus of goods.
Exam-Critical Definitions
Pareto Efficiency
A situation where you cannot improve one person’s well-being without making someone else worse off. It is a “weak” criterion because it does not account for fairness.
Deadweight Loss
The loss of total surplus that occurs when the market is not at a competitive equilibrium (often due to taxes or price controls).
Utilitarianism
A criterion that defines society’s well-being as the “greatest happiness for the greatest number.” It is consequentialist, meaning it only looks at outcomes, not the fairness of the process.