Perfect Competition Notes

Introduction to Perfect Competition
  • Definition: A market structure where no individual buyer or seller can influence the market price.
Characteristics of Perfectly Competitive Markets
  • Price Takers: Buyers and sellers cannot affect prices.
  • Standardized Goods: All products offered are identical.
  • Full Information: All market participants have complete awareness of prices and technology.
  • No Transaction Costs: There are no costs associated with buying or selling.
Revenue Calculation in a Competitive Market
  • Producers can sell unlimited quantities without affecting price.
  • Total Revenue (TR): TR=PimesQTR = P imes Q (Price times Quantity Sold)
  • Average Revenue (AR): AR = rac{TR}{Q} (Total Revenue divided by Quantity Sold)
  • Marginal Revenue (MR): MR = rac{ riangle TR}{ riangle Q} (Change in Revenue divided by Change in Quantity)
  • Relationship: In perfect competition, P=MR=ARP = MR = AR.
Profit Maximization
  • Firms maximize profits by producing the quantity where Marginal Revenue (MR) equals Marginal Cost (MC):
    MR=MCMR = MC
  • Firms can adjust output to reach this equilibrium.
Decision-Making: Shutdown vs. Exit
  • Short-run: Determine if to shut down based on TR compared to variable costs; fixed costs are irrelevant in the short-run as they are sunk.
  • Long-run: If average total cost (ATC) exceeds price (P), firms should exit the market.
Short-run Supply Curve and Shutdown Rule
  • A firm should not produce if the price is below the average variable cost (AVC):
    P < AVC
  • When P > AVC, firms will produce, following the rule of setting P=MCP = MC.
Long-run Supply Curve
  • In the long run, firms can enter or exit the market freely, adjusting the supply curve accordingly.
  • If P > ATC, profits will attract new firms, shifting the supply curve outward until P equals ATC.
  • Conversely, if P < ATC, firms will exit, decreasing supply until equilibrium is restored at zero economic profit.
Long-run Economic Profits
  • Firms earn zero economic profit when operating at the minimum average total cost
    (P = min(ATC)).
  • More efficient firms with lower ATC can earn positive economic profits.
Effects of Demand Shifts
  • An increase in demand causes:
    1. Higher prices leading to short-run profits.
    2. New entrants increase supply, adjusting back to long-run equilibrium prices.
Summary of Key Points
  • Perfectly competitive markets involve many buyers and sellers, standardized products, and no barriers to entry.
  • Profits are maximized when MR=MCMR = MC.
  • In the long-run, firms that earn profits attract more competitors until profits are zero.
  • Supply tends to be perfectly elastic in a truly competitive market, barring differences in production costs among firms.