替代效应和收入效应.pdf

EANDSUBSTITUTIONEFFECTSByWALTERNICHOLSONSlidespreparedbyLindaGhent(EasternIllinoisUniversity)ModifiedbyHuihuaNIE(RenminUnversityofChina):Preference----convexset,utilityfunction,:Maximization----indifferencecurveandbudgetconstraint,----eandprice,Px->XandPy->X2DemandFunctions•Theoptimallevelsofx1,x2,…,e,whichisMarshalldemandfunction•eareexogenousx1*=d1(p1,p2,…,pn,I)x*=x(px,py,I)y*=y(px,py,I)parativestatics?3Homogeneity•e,theoptimalquantitiesdemandedwillnotchange–thebudgetconstraintisunchanged0xi*=tdi(p1,p2,…,pn,I)=di(tp1,tp2,…,tpn,tI)•e4Homogeneity•WithaCobb-Douglasutilityfunctionutility=U(x,y)=*y*ptxpy•ewouldleavex*andy*e•ewillcausethebudgetconstraintoutinaparallelfashiongivenpricesdon’tchange•Sincepx/pydoesnotchange,e•erises,xandyarenormalgoods,xi/Ierises,e•erises,ood,xi/I<erises,urvesdonothavetobe“oddly”’sPrice•Achangeinthepriceofagoodalterstheslopeofthebudgetconstraint–italsochangestheMRSattheconsumer’sutility-maximizingchoices•Whenthepricechanges,eintoplay–substitutioneffect–eeffectChangesinaGood’sPrice•Eveniftheindividualremainedonthesameindifferencecurvewhenthepricechanges,hisoptimalchoicewillchangebecausetheMRSmustequalthenewpriceratio–thesubstitutioneffect•Thepricechangealterstheindividual’s“real”eandthereforehemustmovetoanewindifferencecurve–eeffect0