动态新凯恩斯模型精.ppt
动态新凯恩斯模型第1页，本讲稿共45页OverviewPart B examines a model of an imperfectly competitive economy at a point in timeStart with small nominal frictions in a static modelExtending the static model of imperfect competition to a dynamic setting第2页，本讲稿共45页A Baseline of the ModelAssumptions:Time is discreteImperfectly competitive firms Labor is the firms only input No government;No capital(aggregate consumption and aggregate output are equal)Neglect uncertainly第3页，本讲稿共45页A Baseline of the ModelMarket Behaviors:Households maximize utility,taking the real wage and the real interest rate as given第4页，本讲稿共45页A Baseline of the ModelMarket Behaviors:Households maximize utility,taking the real wage and the real interest rate as givenFirms maximize the present discounted value of their profits,subject to constraints on their price-setting第5页，本讲稿共45页A Baseline of the ModelMarket Behaviors:Households maximize utility,taking the real wage and the real interest rate as givenFirms maximize the present discounted value of their profits,subject to constraints on their price-settingA central bank determines the path of the real interest rate through its conduct of monetary policy第6页，本讲稿共45页Household BehaviorFixed number and infinitely lived householdsObtain utility from consumption and disutility from working第7页，本讲稿共45页Household BehaviorThe representative households object function:第8页，本讲稿共45页Household BehaviorThe representative households object function:satisfies ,第9页，本讲稿共45页Household BehaviorThe representative households object function:satisfies ,is households discount factor,第10页，本讲稿共45页Household BehaviorThe representative households object function:satisfies ,is households discount factor,takes the form:第11页，本讲稿共45页Household BehaviorThe first-order condition for labor supply in period t:第12页，本讲稿共45页Household BehaviorThe first-order condition for labor supply in period t:In equilibrium and both equal ,we can write(6.61)into:第13页，本讲稿共45页Household BehaviorThe first-order condition relating and :where is the real interest rate from to 第14页，本讲稿共45页Household BehaviorThe first-order condition relating and :where is the real interest rate from to Taking logs of both sides solving for :第15页，本讲稿共45页Household BehaviorFor small values of ,第16页，本讲稿共45页Household BehaviorFor small values of ,第17页，本讲稿共45页Household BehaviorRecall,Consumption and output must be equal in equilibrium,and第18页，本讲稿共45页Household BehaviorRecall,Consumption and output must be equal in equilibrium,and第19页，本讲稿共45页Household BehaviorRecall,Consumption and output must be equal in equilibrium,and第20页，本讲稿共45页Firm BehaviorFirm i in period tThe production function:The demand function:第21页，本讲稿共45页Firm BehaviorThe demand function:第22页，本讲稿共45页Firm BehaviorFirm i in period tThe real profits:第23页，本讲稿共45页Firm Behavior :the probability that the price the firm sets in period 0 is in effect in period t第24页，本讲稿共45页Firm Behavior :the probability that the price the firm sets in period 0 is in effect in period tThe marginal utility of the representative households consumption in period t relative to period 0 is:第25页，本讲稿共45页Firm BehaviorRecall,The marginal utility of the representative households consumption in period t:Thus,period t relative to period 0 is:第26页，本讲稿共45页Firm BehaviorThe objective function:is the firms profits in period t if is still in effectThe firm chooses its price to maximize 第27页，本讲稿共45页Firm BehaviorRewrite as:第28页，本讲稿共45页Firm BehaviorTwo assumptions:inflation is low,the economy is always close to its flexible-price equilibrium is close to 1第29页，本讲稿共45页Firm BehaviorRecall equation(6.40):第30页，本讲稿共45页Firm BehaviorRecall equation(6.40):Recall :第31页，本讲稿共45页Firm BehaviorRecall equation(6.40):Recall :第32页，本讲稿共45页Firm BehaviorRecall:第33页，本讲稿共45页Firm BehaviorWhen:第34页，本讲稿共45页Firm BehaviorRecall:第35页，本讲稿共45页Firm BehaviorRecall:第36页，本讲稿共45页Firm BehaviorRecall:Maximize V can be simplified to:第37页，本讲稿共45页Firm BehaviorRecall:First-order condition for :measures the importance of in period to the choice of 第38页，本讲稿共45页Firm BehaviorRecall:Under uncertainty:where denotes expectations as of period 0 第39页，本讲稿共45页Firm BehaviorRecall equation(6.45):The profit-maximizing log price takes the form:Let ,we get:第40页，本讲稿共45页Firm BehaviorRecall:Then:第41页，本讲稿共45页The Central BankThe aggregate supply side:The aggregate demand side:Bring into monetary policy to determine the real interest rate第42页，本讲稿共45页The Central BankTwo approaches:One approach is the central bank follows some rules when sets the real interest rate The other approach is taking the path of nominal GDP as givenThis model choose the second approach 第43页，本讲稿共45页VariationsExtensions of the model:On the central bank and monetary side,to derive the central banks behavior from optimizationOn the monetary side,to explicitly include moneyOn the aggregate side,to introduce investment and governmentOn accuracy side,consider approximations accuracy第44页，本讲稿共45页Thanks!第45页，本讲稿共45页
