宏观经济学consumption参考.pptVIP

consumption 在本章，你将学到以下内容… 最经典消费理论的介绍, 包括: John Maynard Keynes: consumption and current income Irving Fisher: intertemporal choice Franco Modigliani: the life-cycle hypothesis Milton Friedman: the permanent income hypothesis Robert Hall: the random-walk hypothesis David Laibson: the pull of instant gratification Keynes’s conjectures 1. 0 MPC 1 2. Average propensity to consume (APC ) falls as income rises.(APC = C/Y ) 3. 收入是消费的主要决定因素。 The Keynesian consumption function The Keynesian consumption function Early empirical successes: Results from early studies 有更高收入的家庭: 消费更多, ? MPC 0 储蓄更多, ? MPC 1 其收入的大部分被储蓄起来, ? APC ? as Y ? 收入和消费之间有很强的联系Very strong correlation : ? income seemed to be the main  determinant of consumption Problems for the Keynesian consumption function Based on the Keynesian consumption function, 经济学家预测C would grow more slowly than Y over time. 这一预测并不是真实的: 当收入上升，APC 没有下降，并且 C 和收入以相同速度在增长。 Simon Kuznets 表明C/Y 在长时间序列数据表现得very stable。 The Consumption Puzzle Irving Fisher and Intertemporal Choice 许多关于消费理论工作的基础. 假定消费者是forward-looking 并且选择当期和未来时期的消费来最大化终生效用。 消费者选择受到an intertemporal budget constraint, 为当期和未来消费提供所有资源的衡量尺度。 The basic two-period model Period 1: the present Period 2: the future Notation Y1, Y2 = income 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) Deriving the intertemporal budget constraint The intertemporal budget constraint The intertemporal budget constraint The intertemporal budget constraint Consumer preferences Consumer preferences Optimization How C responds to changes in Y Keynes vs. Fisher Keynes: 当期消费仅仅取决于当期的收入。 Fisher: 当期的消费仅取决于终生收入的现值，由于消费者可以跨期借贷，获得收入的时间是无关紧要的。 How C responds to changes in r How C responds to changes in r income effect: 如果消费者是储蓄者，r 的上升makes him better off，会使得两期的消费都增加。 substitution effect: r 的上升会增加当期消费的机会成本，导致 C1 的减少和 C2增加。 Both effects ? ?C2. Whether C1 rises or falls depends on the rel