布兰查德 宏观经济学 ppt 第16章

2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,2 of 26,凯恩斯消费理论的回顾（传统的消费理论）Ks消费理论的推论边界消费倾向只很大，消费与收入具有同样强度的波动性所描述的消费者只考虑眼前，目光短浅（非理性）,凯恩斯消费理论的回顾, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,3 of 26,有关消费的更多的经验事实, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,4 of 26,现代消费理论的核心：消费者是理性的。既考虑现在也考虑将来。希望维持消费的平稳（生活标准不剧烈变动）假定今年起活100年，今年收入为Ynow，以后每年的收入为Ylater。如果你是理性的消费者，如何安排每年的消费？如果今年收入提高1000元，每年消费提高多少？相应的边际消费倾向称为短期*，为多少？如果今年和以后每年都提高1000元，消费提高多少？长期边际消费倾向为多少？你的结论和上面的图相比较，结果如何？结论：消费对收入短期波动反应不大，对收入长期的变动反应大。消费比较平稳。, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,5 of 26,Consumption,The theory of consumption was developed by Milton Friedman in the 1950s, who called it the permanent income theory of consumption, and by Franco Modigliani, who called it the life cycle theory of consumption.,16-1,Up Close and Personal: Learning from Panel Data Sets,Panel data sets are data sets that show the value of one or more variables for many individuals or many firms over time., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,6 of 26,The Very Foresighted Consumer,A very foresighted consumer who decides how much to consume based on the value of his total wealth, which comprises:The value of his nonhuman wealth, or the sum of financial wealth and housing wealth.The value of his human wealth and nonhuman wealth together gives an estimate of his total wealth., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,7 of 26,An Example,Building on what you saw in Chapter 14, lets compute the present value of your labor income as the value of real expected after-tax labor income, discounted using real interest rates.Your wealth today, the expected value of your lifetime after-tax labor income, is around $2 million., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,8 of 26,Toward a More Realistic Description,The constant level of consumption that a consumer can afford equals his total wealth divided by his expected remaining life.Consumption depends not only on total wealth but also on current income.,human wealth, or the expected present value of after-tax labor income,real taxes in year t.,real labor income in year t., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,9 of 26,Toward a More Realistic Description,In words:Consumption is an increasing function of total wealth, and also an increasing function after-tax labor income. Total wealth is the sum of nonhuman wealth financial wealth plus housing wealth and human wealth the present value of expected after-tax income., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,10 of 26,Putting Things Together: Current Income, Expectations, and Consumption,Expectations affect consumption in two ways:Directly through human wealth, or expectations of future labor income, real interest rates, and taxes.Indirectly through nonhuman wealth - stocks, bonds, and housing. Expectations of the value of nonhuman wealth is computed by financial markets., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,11 of 26,Do People Save Enough for Retirement?, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,12 of 26,Putting Things Together: Current Income, Expectations, and Consumption,This dependence of consumption on expectations has two main implications for the relation between consumption and income:Consumption is likely to respond less than one for one to fluctuations in current income.Consumption may move even if current income does not change.Consumption may move even if current income does not due to changes in consumer confidence., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,13 of 26,Investment,Investment decisions depend on current sales, the current real interest rate, and on expectations of the future.The decision to buy a machine depends on the present value of the profits the firm can expect from having this machine versus the cost of buying it.,16-2, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,14 of 26,Investment and Expectations of Profit,Depreciation:The rate of depreciation, , measures how much usefulness the machine loses from one year to the next.Reasonable values for are between 4 and 15% for machines, and between 2 and 4% for buildings and factories., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,15 of 26,The Present value of Expected Profits,V(et): The present value, in year t, of expected profit in year t+1 equals:,In year t+2,In year t, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,16 of 26,The Present value of Expected Profits,Computing the Present Value of Expected Profits,Figure 16 - 1, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,17 of 26,The Investment Decision,Denote It as aggregate investment, t as profit per machine (or per unit of capital) for the economy as a whole, and V(et) as the expected present value of profit per unit of capital. This yields the investment function:,In words: Investment depends positively on the expected present value of future profits (per unit of capital)., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,18 of 26,Economists call such expectations expectations that the future will be like the present static expectations. Under these two assumptions, we get,A Convenient Special Case,Suppose firms expect both future profits and future interest rates to remain at the same level as today, so that,and, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,19 of 26,Tobins q denotes the variable corresponding to the value of a unit of capital in place relative to its purchase price.,Investment and the Stock Market,Figure 1,Tobins q. Versus the Ratio of Investment to Capital: Annual Rates of Change, 1960-1999, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,20 of 26,A Convenient Special Case,Putting and together give us an equation for investment:,The sum of the real interest rate and the depreciation rate is called the user cost or the rental cost of capital.Therefore,Rental Cost, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,21 of 26,Current Versus Expected Profit,Investment depends on expected future profit, but also moves strongly with fluctuations in current profit.,Firms may be reluctant to borrow if current profit is low. But if current profit is high, the firm may not need to borrow to finance its investments. Even if the firm wants to invest, it might have difficulty borrowing. Potential lenders may not be convinced the project is as good as the firms says., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,22 of 26,Current Versus Expected Profit,Changes in Investment and Changes in Profit in the United States since 1960,Investment and profit move very much together.,Figure 16 - 2, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,23 of 26,Profitability refers to the expected present discounted value of profits.Cash flow refers to current profit, or the net flow of cash the firm is receiving.Both profitability and cash flow are important for investment decisions, and are likely to move together.,Profitability Versus Cash Flow, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,24 of 26,Profits and Sales,Changes in Profit per Unit of Capital Versus Changes in the Ratio of Output to Capital in the United States since 1960,Profit and the ratio of output to capital move largely together.,Figure 16 - 3, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,25 of 26,The Volatility ofConsumption and Investment,Lets look at the similarities between our treatment of consumption and of investment behavior:Whether consumers perceive current movements in income to be transitory or permanent affects their consumption decisions.In the same way, whether firms perceive current movements in sales to be transitory or permanent affects their investment decisions.,16-3, 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,26 of 26,The Volatility ofConsumption and Investment,But there are also important differences between consumption decisions and investment decisions:When faced with an increase in income that consumers perceive as permanent, they respond with at most an equal increase in consumption.When firms are faced with an increase in sales they believe to be permanent, their present value of expected profits increases, leading to an increase in investment., 2006 Prentice Hall Business Publishing Macroeconomics, 4/e Olivier Blanchard,27 of 26,The Volatility ofConsumption a