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1、slide 1InvestmentInvestmentslide 2In this chapter, you will learn解释每一类型投资的主要理论。 why investment is negatively related to the interest rate为什么投资与利息率是负相关的 things that shift the investment function投资函 数移动的因素 why investment rises during booms and falls during recessions为什么在经济繁荣时期投资上 升，在经济衰退时期投资会下降。Invest
2、mentslide 3Three types of investmentBusiness fixed investment固定资产投资: businesses spending on equipment and structures for use in production. Residential investment居住投资: purchases of new housing units (either by occupants or landlords). Inventory investment存货投资: the value of the change in inventories
3、of finished goods, materials and supplies, and work in progress.Investmentslide 4U.S. investment and its componentsBillions of 1996 dollars-25002505007501000125015001750200019701975198019851990199520002005Total investmentBusiness fixed investment Residential investment Change in inventoriesInvestmen
4、tslide 5Understanding business fixed investment固定资产投资的标准模型The standard model of business fixed investment: the neoclassical model of investment表明投资取决于 MPK interest rate tax rules affecting firmsInvestmentslide 6Two types of firmsFor simplicity, 假定有两种类型: 1. Production firms rent the capital they use
5、to produce goods and services.租用资本来生产商 品和服务。 2. Rental firms own capital, rent it to production firms.拥有资本，将资本出租给生产企 业投资是租赁企业在新资本品上的支出。 “investment” is the rental firms spending on new capital goods.Investmentslide 7The capital rental market生产企业必须决定租 用多少资本.Recall from Chap. 3: 竞争性企业在 MPK = R/P这一点上 租
6、用资本. K capital stockreal rental price, R/Pcapital supplycapital demand (MPK) equilibrium rental rateInvestmentslide 8Factors that affect the rental priceFor the Cobb-Douglas production function, the MPK (and hence equilibrium R/P ) isThe equilibrium R/P would increase if: K (e.g., earthquake or war)
7、 L (e.g., pop. growth or immigration) A (technological improvement)Investmentslide 9Rental firms investment decisionsRental firms invest in new capital when the benefit of doing so exceeds the cost当投资新资 本品的收益大于成本时，租赁企业会投资新资本. The benefit (per unit capital): R/P, the income that rental firms earn fro
8、m renting the unit of capital to production firms租赁企业将一单位资本品租给生 产企业所赚得的收入。Investmentslide 10The cost of capitalComponents of the cost of capital资本品成本的内 容:interest cost: i PK,where PK = nominal price of capitaldepreciation cost: PK,where = rate of depreciationcapital loss: PK (a capital gain, PK 0, r
9、educes cost of K )The total cost of capital is the sum of these three parts:Investmentslide 11Then, interest cost = depreciation cost = capital loss = total cost =The cost of capitalExample: car rental company (capital: cars)假定 PK = $10,000, i = 0.10, = 0.20, and PK/PK = 0.06 Nominal costof capital$
10、1000 $2000 $600$2400Investmentslide 12The cost of capitalFor simplicity, 假定 PK/PK = . 整体通货膨胀率 Then, the nominal cost of capital equalsPK(i + ) = PK(r + ) and the real cost of capital equalsThe real cost of capital depends positively on: the relative price of capital 资本品的相对价格 the real interest rate 实
11、际利息率 the depreciation rate 折旧率Investmentslide 13The rental firms profit rateA firms net investment depends on its profit rate:If profit rate 0, then increasing K is profitable增加K是有利可图的。If profit rate 1, 企业购买更多的资本品来提高企业 的市场价值。 If q cost of capital, 利润高，该企业的 股票市场价值上升，意味着a high value of q. If MPK produ
12、ction, inventories fall. Investmentslide 37Motives for holding inventories1. production smoothing2. inventories as a factor of productionInventories allow some firms to operate more efficiently. samples for retail sales purposesspare parts for when machines break downInvestmentslide 38Motives for ho
13、lding inventories1. production smoothing2. inventories as a factor of production3. stock-out avoidance 避免脱销To prevent lost sales when demand is higher than expected. Investmentslide 39Motives for holding inventories1. production smoothing2. inventories as a factor of production3. stock-out avoidance
14、4. work in processGoods not yet completed are counted in inventory. Investmentslide 40The Accelerator Model加速模型A simple theory that explains the behavior of inventory investment, without endorsing any particular motiveInvestmentslide 41The Accelerator ModelNotation: N = stock of inventories N = inve
15、ntory investmentAssume: Firms hold a stock of inventories proportional to their outputN = Y, where is an exogenous parameter reflecting firms desired stock of inventory as a proportion of output. Investmentslide 42The Accelerator ModelResult: I=N = Y Inventory investment is proportional to the chang
16、e in output. 当产出增加时，企业增加存货，存货投 资为正。 当产出下降时，企业存货下降，存货投 资是负的。Investmentslide 43Evidence for the Accelerator ModelInventory investment (billions of 1996 dollars)Change in real GDP (billions of 1996 dollars)-40-20020406080100-200-10001002003004005001982200120041998198419781996198319671974Investmentslide 44Inven
