北大微观经济学课件(英文版)ch4 Utility.ppt

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1、ChapterFourUtility效用2021/8/29中级微观经济学StructureUtilityfunction(效用函数）DefinitionMonotonictransformation（单调转换）ExamplesofutilityfunctionsandtheirindifferencecurvesMarginalutility（边际效用）Marginalrateofsubstitution边际替代率MRSaftermonotonictransformation2021/8/29中级微观经济学UtilityFunctionsAutilityfunctionU(x)r

2、epresentsapreferencerelationifandonlyif:x’x”U(x’)>U(x”)x’x”U(x’)

3、tilityFunctions&Indiff.CurvesConsiderthebundles(4,1),(2,3)and(2,2).Suppose(2,3)(4,1)~(2,2).Assigntothesebundlesanynumbersthatpreservethepreferenceordering;e.g.U(2,3)=6>U(4,1)=U(2,2)=4.Callthesenumbersutilitylevels.p2021/8/29中级微观经济学UtilityFunctions&Indiff.CurvesAnindifferencecurvecontainsequal

4、lypreferredbundles.Equalpreferencesameutilitylevel.Therefore,allbundlesinanindifferencecurvehavethesameutilitylevel.2021/8/29中级微观经济学UtilityFunctions&Indiff.CurvesSothebundles(4,1)and(2,2)areintheindiff.curvewithutilitylevelUº4Butthebundle(2,3)isintheindiff.curvewithutilitylevelUº6.Onanindiff

5、erencecurvediagram,thispreferenceinformationlooksasfollows:2021/8/29中级微观经济学UtilityFunctions&Indiff.CurvesUº6Uº4(2,3)(2,2)~(4,1)x1x2p2021/8/29中级微观经济学UtilityFunctions&Indiff.CurvesComparingmorebundleswillcreatealargercollectionofallindifferencecurvesandabetterdescriptionoftheconsumer’spreferenc

6、es.2021/8/29中级微观经济学UtilityFunctions&Indiff.CurvesUº6Uº4Uº2x1x22021/8/29中级微观经济学UtilityFunctions&Indiff.CurvesThecollectionofallindifferencecurvesforagivenpreferencerelationisanindifferencemap.Anindifferencemapisequivalenttoautilityfunction;eachistheother.2021/8/29中级微观经济学UtilityFunctionsThereis

7、nouniqueutilityfunctionrepresentationofapreferencerelation.SupposeU(x1,x2)=x1x2representsapreferencerelation.Againconsiderthebundles(4,1),(2,3)and(2,2).2021/8/29中级微观经济学UtilityFunctionsU(x1,x2)=x1x2,soU(2,3)=6>U(4,1)=U(2,2)=4;thatis,(2,3)