经济学原理·萨缪尔森--中山大学岭南学院ch(1).ppt

,CH.8. Analysis of Perfectly Competitive Markets,A.Supply Behavior of the Competitive Firm,the Competitive Firm: maximizes profits profits=total revenues-total costs,the Competitive Firm:,price-taker faces a completely horizontal demand curve the extra revenue gained from each extra unit sold is the market price,Demand Curve Is Completely Elastic for a Perfectly Competitive Firm,Supply Decision of Competitive Firm,The maximum profit output comes at that output where marginal cost equals price. MC=P,Firms Supply curve,Firms Supply Curve Travels Down the MC Curve to the Shutdown Point.,Firms Supply Curve Is Its Rising Marginal Cost Cure,Firms Supply Curve Travels Down the MC Curve to the Shutdown Point,M：zero-profit point (零利润点) P=AC=MC M: shutdown point （停业点） P=AVC=MC,B. Supply Behavior in Competitive Industries,market supply curve: horizontally add all firms supply curves,Add All Firms Supply Curves to Derive Market Supply,Short-run and long-run equilibrium,Short-run equilibrium: use the same fixed amount of plant and equipment. Long-run equilibrium: all factors are variable.,Effect of Increase in Demand on Price Varies in Different Time Periods,The long run for a competitive industry,Zero-profit long-run equilibrium: P= MC = minimum long run AC = zero-profit price The long run equilibrium in a competitive industry is one with no economic profits.,Long-Run Industry Supply Depends on Cost Conditions,C. Special Cases of Competitive Markets,demand rule: demand for a commodity , the price demand , the quantity demanded supply rule: supply of a commodity , the price , the quantity bought and sold ,Constant cost Increasing costs and diminishing returns Fixed supply and economic rent Backward-bending supply curve,Constant-Cost Case,Increasing costs and diminishing returns,Factors with Fixed Supply Earn Rent,Backward-Bending Supply Curve,Shifts in supply,An increased supply will decrease P most when demand is inelastic. An increased supply will increase Q most when demand is inelastic.,D. Efficiency and Equity of Competitive Markets,the concept of efficiency,Efficiency of Competitive Equilibrium,The marginal gain to society from the last unit consumed = the marginal cost to society of that last unit produced,At Competitive Equilibrium Point E, the Marginal Costs and Utilities of Food Are Exactly Balanced,Producer Surplus Economic Surplus=CS+PS,Equilibrium with many consumers and markets,The willingness of people possessing dollar vote to pay goods as represented by demand with the marginal costs of those goods as represented by firms supply Under certain conditions, competition guarantees efficiency_no consumers can be raised without lowering another consumers utility.,Competitive Market Integrates Consumers Demands and Producers Costs,the cen