General Equilibrium (cont)
Big ideas: Tuesday: Edgeworth box Pareto efficiency (normative theory) Today: Competitive equilibrium (positive theory) First welfare theorem
Edgeworth Box OB OA
Desirable Allocation: Pareto Efficient Allocation x Pareto efficient, if there does not exist allocation y that is A) at least as good as x for all B) is strictly better for at least one Pareto efficiency = equality of MRS All Pareto efficient allocations=contract curve
Pareto efficiency OB OA
Competitive (Walrasian) Equilibrium Competitive Equilibrium A positive model of free market economy Walras, then Arrow and Debreu Extensively used by ``practitioners’’
Competitive (Walrasian) Equilibrium Consider Individuals respond optimally to prices Prices are such that markets clear We call a competitive equilibrium
Excess supply, Demand OB OA
Excess Demand, Supply, Equilibrium OB OA
Excess Demand, Supply, Equilibrium OB OA
Cobb-Douglass Calculation Equilibrium = 6 numbers 3 tricks that simplify calculation Market clearing for one market (Walras Law) Use Magic Formulas Solve for relative price (only)
Cobb-Douglass general
Example
Geometry OB OA
Invisible Hand (Adam Smith) Are markets (Pareto) efficient? First Welfare Theorem: allocation in Competitive equilibrium is Pareto optimal Proof OB OA
Other Preferences Quasilinear Perfect complements