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Review of Results from Double Auctions • 20 different markets • 10 buyers and 10 sellers in each market – the 5 buyers and 5 sellers on page 178-179 plus their clones – Prediction: P = $13 and Q = 26 – results were very close to prediction • For $6 increase in MC, the equilibrium price P = $16 and equilibrium Q = 20 Properties of Competitive Markets • One price in the market which is the equilibrium price P • Each firm produces a quantity such that MC equals the equilibrium price P – Hugo, Mimi,... • Each consumer buys a quantity such that MB equals the equilibrium price P – Maria, Ken,... Are Competitive Markets Efficient • Definition (need to be careful) • Pareto efficiency: – a situation where it is impossible to make one person better off without hurting another person Conditions for Pareto Efficiency • marginal benefit equals marginal cost (for last item produced) • marginal cost of each good should be the same for all producers • marginal benefit of each good should be the same for all consumers Are the conditions satisfied for a competitive market? Check ‘em – first: MC = MB because equilibrium occurs at the intersection of the demand (MB) curve and the supply (MC) curve – second: MB = P for each consumer, because each consumer sets MB = P and because there is a single equilibrium price P in the market equilibrium – third: MC = P for each firm, because each firm sets MC = P and because there is a single equilibrium price P in market equilibrium Answer: YES! ALL THREE CONDITIONS ARE SATISFIED 07_06 PRICE Market supply (derived from firms' marginal costs) Market demand (derived from consumers' marginal benefits) D E F Too little Efficient Too much QUANTITY We can measure how well the market works: • Use producer and consumer surplus • in an equilibrium of a competitive market the sum of producer surplus and consumer surplus is as large as possible • OR, the marginal benefit less the marginal cost of all items produced is as large as possible • Or, Deadweight Loss is eliminated 07_07 PRICE Deadweight loss: area A + B Supply A Market price B Demand QUANTITY Too little PRICE Supply Market price Demand QUANTITY Efficient PRICE Supply C D Market price Negative producer surplus and negative consumer surplus: area C + D Demand QUANTITY Too much Deadweight Loss from a Tax • A tax on firms raises the marginal cost for each firm • Supply curve shifts up by the amount of the tax • Quantity produced falls • Price rises, but by less than the tax • Deadweight loss is created 07_08A PRICE New supply curve Old supply curve Deadweight loss New price Amount of sales tax Price rises by this amount. Old price Price received by sellers after sending tax to government Demand curve QUANTITY New quantity Old quantity Quantity declines by this amount. Deadweight Loss from a Sales Tax