消费投资与储蓄.ppt

,消费、投资与储蓄Consumption ，Investment and Saving,第24章 Chapter 24 (对应教材24，25，26）,GDP的构成 The Composition of GDP,消费 Consumption (C) 投资 Investment (I) 政府支出 Government Spending (G) 净出口 Net Exports (X Q) 库存投资 Inventory Investment (Is),消费 Consumption,消费代表消费者购买的物品与服务。 Consumption (C) represent goods and services purchased by consumers. 食物，机票，度假，新车， Food, airline tickets, vacations, new cars,投资 Investment,投资有时被称作固定投资，以区别于库存投资 Investment (I) is sometimes called fixed investment to distinguish it from inventory investment. 投资是非居民投资和居民投资之和。前者指企业对于新工厂与及其的购买（例如涡轮机、计算机），后者指人们对于新房屋或公寓的购买 Investment is the sum of nonresidential investment, the purchase by firm of new plants or new machines (from turbine to computers), and residential investment, the purchase by people of new houses or apartments.,投资 Investment,企业购买机器或者厂房是为了能够在将来生产更多的产出。 Firms buy machines or plants to be able to product more output in the future. 人们购买房屋或者公寓是为了未来得到住房服务。 People buy houses or apartments to get housing services in the future.,政府支出 Government Spending,政府支出代表联邦、州和地方政府购买的物品和服务 Government Spending, (G), represents the purchase of goods and services by the federal, state, and local governments. 物品包括飞机到办公设备。 The goods range from airplanes to office equipment. 服务包括政府雇员提供的服务。 The services include services provided by government employees. 实际上，国民收入帐户认为是政府购买了政府雇员提供的服务 然后免费提供给公众。 In effect, the national income accounts treat the government as buying the services provided by government employee and then providing these services to the public, free of charge.,政府支出 Government Spending,G不包括政府转移支付，例如医疗保险或者社会保险，也不包括政府支付的债务利息。 G does not include government transfers, such as Medicare or Social Security, nor interest payments on the government debt. 虽然这些属于政府的开支，但他们不是对于物品和服务的购买。 Although these are clearly government expenditures, they are not purchases of goods and services.,净出口 Net Exports,进口代表消费者、企业或者政府购买的外国的物品和服务。 Imports (Q) represents the purchases of foreign goods and services by U.S. consumers, U.S. firms, and the U.S. government. 出口代表外国购买的本国的物品和服务。 Exports (X) represents the purchases of U.S. goods and services by foreigners. 出口和进口之差被称作净出口，或贸易余额。 The difference between exports and imports, (X Q), is called net exports, or the trade balance.,净出口 Net Exports,如果出口大于进口，一国就有了贸易盈余。 If exports exceed imports, a country is said to run a trade surplus. 如果出口小于进口，该国就有了贸易赤字。 If exports are less than imports, the country is said to run a trade deficit.,库存投资 Inventory Investment,一些物品是某年生产的，但不在该年出售，而是来年出售。一些物品是某年出售的，但却是往年生产的。 Some of the goods produced in a given year are not sold in that year, but sold in later year. Some of the goods sold in a given year may have been produced in an earlier year. 某年的物品生产量与出售量之差被称作库存投资。 The difference between goods produced and goods sold in a given year equivalently, between production and sales is called inventory investment and is denoted Is.,库存投资 Inventory Investment,如果生产大于销售，企业积累库存。库存投资是正的。 If produce exceeds sales, firm accumulate inventories. Inventory investment is positive. 如果生产小于销售，企业减少库存。库存投资为负。 If produce is less than sales, firms decrease inventories. Inventory investment is negative.,消费的决定因素 The Determination of Consumption,消费的主要决定因素显然是收入，更准确的说，是可支配收入，即消费者在得到来自政府的转移支付并支付税收后剩下的收入。 The main determinant of consumption (C) is surely income, or more precisely disposable income (YD), the income that remains once consumers have received transfers from the government and paid their taxes. C = C(YD) (+) 函数C(YD) 被称作消费函数。 The function C(YD) is called the consumption function.,消费的决定因素 The Determination of Consumption,经济学家把这样的方程叫做行为方程，因为这一方程反映了某些方面的行为这里是消费者的行为。 Economists call such an equation a behavioral equation, to indicate that the equation reflect some aspect of behavior in this case, the behavior of consumers.,消费的决定因素 The Determination of Consumption,假定消费函数是线性的。 Assume that the consumption function is a linear relation. C = c0 + c1YD 参数c1被称作（边际）消费倾向。00. 如果收入为零，人们通过动用储蓄卖掉现有资产来保持正的消费。 People have positive consumption if their income is zero by dissaving by selling some of their assets, or by borrowing.,消费的决定因素 The Determination of Consumption,消费的决定因素 The Determination of Consumption,可支配收入等于： Disposable income is given by YD Y T 这里Y是收入，T是税收减去消费者得到的政府转移支付。 where Y is income and T is taxes paid minus government transfers received by consumers. 这是一个恒等式。 This equation is an identity. C = c0 + c1(Y T),为什么价格不再是决定消费的主要因素？,在微观经济学中，消费者对某一物品的需求取决于它的相对价格，即它相对于其他物品的价格。 在宏观经济学中，所有物品（看成一种物品）的消费需求与整体物价水平的关系，最终体现在物价水平对消费者的购买力实际收入的影响当中。,投资的决定因素 The Determination of Investment,我们将投资视为给定，写成： We shall take investment as given, and write,投资的决定因素 The Determination of Investment,模型有两类变量： Models have two types of variables. 一些变量依赖于模型中的其他变量，因而在模型内得到解释内生变量。例如，消费。 Some variables depend on other variables in the model, and are therefore explained within the model Endogenous variables. E.g., consumption (C) 另外一些变量不在模型内进行解释而是给定的 外生变量。例如，投资。 Other variables are not explained within the model but are instead taken as given Exogenous variables. E.g., investment (I),投资等于储蓄：考虑物品市场均衡的另一方法 Investment Equals Saving: An Alternative Way of Thinking About Goods-Market Equilibrium,到目前为止我们考虑均衡都是关注的供给与需求之间的相互作用。 Thus far we have thought about equilibrium in terms of interaction between the supply and the demand for goods. 另一考虑均衡的等价方法是关注投资与储蓄。 An alternative but equivalent way of thinking about equilibrium focuses on investment and saving instead.,投资等于储蓄：考虑物品市场均衡的另一方法 Investment Equals Saving: An Alternative Way of Thinking About Goods-Market Equilibrium,私人储蓄，也就是消费者的储蓄，等于可支配收入减去消费。 Private saving (S), saving by consumers, is equal to their disposable income minus their consumption,我们将(1-c1) 称为储蓄倾向。 We call (1-c1) the propensity to save.,投资等于储蓄：考虑物品市场均衡的另一方法 Investment Equals Saving: An Alternative Way of Thinking About Goods-Market Equilibrium,公共储蓄等于税收减去政府支出。 Public saving (T G), is equal to taxes minus government spending.,投资等于储蓄：考虑物品市场均衡的另一方法 Investment Equals Saving: An Alternative Way of Thinking About Goods-Market Equilibrium,投资等于储蓄：考虑物品市场均衡的另一方法 Investment Equals Saving: An Alternative Way of Thinking About Goods-Market Equilibrium,物品市场的均衡要求投资等于储蓄私人储蓄加上公共储蓄之和。 Equilibrium in the goods market requires that investment equals saving the sum of private and public saving. 这一考虑均衡的方法解释了为什么物品市场的均衡条件被称作IS关系（投资和储蓄的首字母）。 This way of looking at equilibrium explains why the equilibrium condition for the goods market is called the IS relation, for “Investment equals Saving.” 储蓄是通过产出的调整来满足既定的投资需求的。 Saving (S) adjusts to meet given investment demand (I) through the adjustment of production (Y).,储蓄悖论 The Paradox of Saving,人们增加储蓄的企图导致产出下降而储蓄不变。 Attempts by people to save more lead both to a decline in output and to unchanged saving. 这一令人吃惊的结果组合被称为储蓄悖论。 This surprising pair of results is known as the paradox of saving,增加储蓄的结果 The Effect of Increasing Saving,增加储蓄的结果 The Effect of Increasing Saving,这一简单模型的结果在短期更适用。 The results of this simple model are of much relevance in the short run. 但在中期或者长期，其他机制慢慢开始起作用，储蓄率的提高有可能导致高储蓄和高产出。 But at the medium and the long run, other mechanisms come into play over time and an increase in the sav