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slide 0 CHAPTER 16 Consumption ?consumption slide 1 CHAPTER 16 Consumption 在本章,你將學到以下內(nèi)容 … 最經(jīng)典消費理論的介紹 , 包括 : ? John Maynard Keynes: consumption and current ine ? Irving Fisher: intertemporal choice ? Franco Modigliani: the lifecycle hypothesis ? Milton Friedman: the permanent ine hypothesis ? Robert Hall: the randomwalk hypothesis ? David Laibson: the pull of instant gratification slide 2 CHAPTER 16 Consumption Keynes’s conjectures 1. 0 MPC 1 2. Average propensity to consume (APC ) falls as ine rises. (APC = C/Y ) 3. 收入是消費的主要決定因素。 slide 3 CHAPTER 16 Consumption The Keynesian consumption function C Y 1 c C C c Y??Cc = MPC = 消費函數(shù)的斜率 slide 4 CHAPTER 16 Consumption The Keynesian consumption function C Y C C c Y??slope = APC 當收入上升,消費者會將其收入的更多部分儲蓄起來,這樣 APC下降 . CC cYY? ? ?A P Cslide 5 CHAPTER 16 Consumption Early empirical successes: Results from early studies ? 有更高收入的家庭 : ?消費更多 , ? MPC 0 ?儲蓄更多 , ? MPC 1 ?其收入的大部分被儲蓄起來 , ? APC ? as Y ? ? 收入和消費之間有很強的聯(lián)系 Very strong correlation : ? ine seemed to be the main determinant of consumption slide 6 CHAPTER 16 Consumption Problems for the Keynesian consumption function ? Based on the Keynesian consumption function, 經(jīng)濟學家預測 C would grow more slowly than Y over time. ? 這一預測并不是真實的 : ?當收入上升, APC 沒有下降,并且 C 和收入以相同速度在增長。 ? Simon Kuzs 表明 C/Y 在長時間序列數(shù)據(jù)表現(xiàn)得 very stable。 slide 7 CHAPTER 16 Consumption The Consumption Puzzle C Y Consumption function from long time series data (constant APC ) Consumption function from crosssectional household data (falling APC ) slide 8 CHAPTER 16 Consumption Irving Fisher and Intertemporal Choice ? 許多關于消費理論工作的基礎 . ? 假定消費者是 forwardlooking 并且選擇當期和未來時期的消費來最大化終生效用。 ? 消費者選擇受到 an intertemporal budget constraint, 為當期和未來消費提供所有資源的衡量尺度。 slide 9 CHAPTER 16 Consumption The basic twoperiod model ? Period 1: the present ? Period 2: the future ? Notation Y1, Y2 = ine in period 1, 2 C1, C2 = consumption in period 1, 2 S = Y1 C1 = saving in period 1 (S 0 if the consumer borrows in period 1) slide 10 CHAPTER 16 Consumption Deriving the intertemporal budget constraint ? Period 2 budget constraint: 22 ( 1 )C Y r S? ? ?2 1 1( 1 ) ( )Y r Y C? ? ? ? Rearrange terms: 1 2 2 1( 1 ) ( 1 )r C C Y r Y? ? ? ? ?? Divide through by (1+r ) to get… slide 11 CHAPTER 16 Consumption The intertemporal budget constraint 221111CYCYrr? ? ???終生消費的現(xiàn)值 終生收入的現(xiàn)值 slide 12 CHAPTER 16 Consumption The intertemporal budget constraint The budget constraint shows all binations of C1 and C2 that just exhaust the consumer’s resources. C1 C2 12 (1 )Y Y r??12(1 )r Y Y??Y1 Y2 Borrowing Saving Consump