货币银行学 21

Part 5 货币理论(Monetary Theory)Chapter 21 货币需求(The Demand For money)在前几章中，我们学习了什么是货币供应、货币供应的决定以及中央银行在货币供应中的作用。

从这一章开始，我们要探讨货币供应在决定价格水平及全部商品和劳务（总产出）中的作用(Now we are ready to explore the role of the money supply in determining the price level and total production of goods and services(aggregate output) in the economy) 关于货币对经济的影响的研究，称为货币理论(the study of the effect of money on the economy is called Monetary Theory)。

When economists mention supply, the word demand is sure to follow.The supply of money is an essential building block in understanding how monetary policy affects the economy because it suggests the factors that influence the quantity of money in the economy.Not surprisingly, another essential parts ofmonetary theory is the demand for money.This chapter describes how the theories of the demand for money have evolved.A central question in monetary theory is whether or to what extent the quantity of money demanded is affected by changes in interest rates. Because this issue is crucial to how we view money’s effects on aggregate economic activity, we focus on the role of interest rates in the demand for money.1.货币数量论(Quantity Theory of Money)The quantity theory of money is a theory of how the nominal value of aggregate income is determined. It also tells us how much money is held for a given amount of aggregate income.A. 货币流通速度和交易方程式(Velocity of Money and Equation of Exchange)The clearest exposition of the classical quantity theory approach is found in the work of the American economist Irving Fisher, in his influential book The Purchasing Power of Money, published in 1911.M×V≡P×Ywhere M = the money supplyV = velocity of moneyP = the price levelY = aggregate output (income)P×Y is also thought of as aggregate nominal income for the economy or as nominal GDP.The equation of exchange states that the quantity of money multiplied by the number of times that this money is spent in a given year must be equal to nominal income (the total nominal amount spent on goods and services in that year).Irving Fisher reasoned that velocity is determined by the institutions in an economy that affect the way individuals conduct transactions.Fish took the view that the institutional and technological features of the economy would affect velocity only slowly over time, so velocity would normally be reasonably constant in the short run.B. 货币数量论(Quantity Theory)For the classical economists (including Fisher), the quantity theory of money provided anexplanation of movements in the price level: Movements in the price level result solely from changes in the quantity of money.Because the classical economists thought that wages and prices were completely flexible, they believed that the level of aggregate of output Y produced in the economy during normal times would remain at the full-employment level, Y in the equation of exchange could also be treated as reasonably constant in the short run.C. 货币需求数量论(Quantity Theory of Money Demand)Because the quantity theory of money tells us how much money is held for a given amount of aggregate income, it is in fact a theory of the demand for money.The equation of exchange can rewrite asM = 1／V×PYWe can replace M in the equation by Md. Using k to represent the quantity 1／V(a constant because the V is a constant), we can rewrite the equation as M d = k ×PYThis equation tells us that because k is a constant,the level of transactions generated by a fixed level of nominal income PY determines the quantity of money M d that people demand. Therefore, Fisher’s quantity theory of money suggests that the demand for money is purely a function of income, and interest rates have no effect on the demand of money.Fisher came to this conclusion because he believed that people hold money only to conduct transactions and have no freedom of action in terms of the amount they want to hold.The demand for money is determined:(1) by the level of transactions generated by the level of nominal income PY and(2) by the institutions in the economy that affect the way people conduct transactions that determine velocity and hence k.2. 剑桥学派的货币需求理论(Cambridge Approach To Money Demand)While Fisher was developing his quantity theory approach to the demand for money, a group of classical economists in Cambridge, England, which included Alfred Marshall and A. C. Pigou, werestudying the same topic. Although their analysis led to an equation identical to Fisher’s money demand equation (M d= k ×PY), their approach differed significantly. Instead of studying the demand for money by looking solely at the level of transactions and institutions that affect the way people conduct transactions as key determinants, the Cambridge economists asked how much money individuals would want to hold.The classic Cambridge economists recognized that two properties of money motivate people to want to hold it: its utility as a medium of exchange and as a store of wealth.(1)Medium of exchangeBecause it is a medium of exchange, people can use money to carry out transactions.The Cambridge economists agree with Fisher that the demand for money would be related to (but not determined solely by) the level of transactions and that there would be a transactions component of money demand proportional to nominal income.(2) Store of wealthThat money also functions as a store of wealth led the Cambridge economists to suggest that the level of people’s wealth also affects the demand for money. As wealth grows, an individual needs to store it by holding a large quantity of assets—one of which is money.Because the Cambridge economists believed that wealth in nominal terms is proportional to nominal income, they also believed that the wealth component of money demand is proportional to nominal income.Concluding that the demand for money would be proportional to nominal income, the Cambridge economists expressed the demand for money function asM d = k ×PYwhere k is the constant of proportionality. Because this equati on looks just like Fisher’s, it would seem that the Cambridge group agree with Fisher that interest rates play no role in the demand for money in the short run. However, that is not the case.Although the Cambridge economists often treated k as a constant and agreed with Fisher that nominal income is determined by the quantity of money. But their approach allowed individuals to choose how much money they wished to hold. It allowed for the possibility that k could fluctuate in the short run because the decisions about using money to store wealth would depend on the yield and expected returns on other assets that also functioned as stores of wealth. If these characteristics of other assets changed, k might change too. Although this seems a minor distinction between the Fisher and Cambridge approaches, you will see that when John Maynard Keynes (a later Cambridge Economist) extended the Cambridge approach, he arrived at a view very different from that of the quantity theorists on the importance of interest rates to the demand for money.To summarize, both Irving Fisher and the Cambridge economists developed a classical approach to the demand for money in which the demand for money is proportional to income.However, the two approaches differ in that Fisher’s emphasized technological factors and ruled out any possible effect of interest rates on the demand for money in the short run, whereas the Cambridge approach emphasized individual choice and did not rule out the effects of interest rates.3. 货币流通速度是一个常数吗(Is velocity a constant)？4. 凯恩斯的流动性偏好理论(Keynes’s Liquidity Preference Theory)In his famous 1936 book The General theory of Employment, Interest, and money, John Maynard Keynes abandoned the classical view that velocity was a constant and developed a theory of money demand that emphasized the importance of interest rates. His theory of the demand for money, which he called the liquidity preference theory, also asked the question, Why do individuals hold money?A. 交易动机(Transactions Motive)Keynes believed that the transactions were proportional to income, like the classical economists, he took the transactions component of the demandfor money to be proportional to income.B. 谨慎动机(Precautionary Motive)Keynes believed that the amount of precautionary money balances people want to hold is determined primarily by the level of transactions that they expect to make in the future and that these transactions are proportional to income. Therefore, he postulated, the demand for precautionary money balances is proportional to income.C. 投机动机(Speculative Motive)If Keynes had ended his theory with the transactions and precautionary motives, income would be the only important determinant of the demand for money, and he would not have added much to the Cambridge approach.Unlike the classical Cambridge economists, who were willing to treat the wealth component of money demand as proportional to income, Keynes believed that interest rates, too, have an important role to play.From Keynes’s reasoning we can conclude that asinterest rates rise, the demand for money falls, and therefore money demand is negatively related to the level of interest rates.D. 三种动机的综合(Putting the Three Motives Together)In putting the three motives for holding money balances together into a demand for money equation, Keynes was careful to distinguish between nominal quantities and real quantities. Money is valued in terms of what it can buy. Keynes thus reasoned that people want to hold a certain amount of real money balances (the quantity of money in real terms)—an amount that his three motives indicated would be related to real income Y and to interest rates i. Keynes wrote down the following demand for money equation, known as the liquidity preference function, which says that the demand for real money balances M d／P is a function of (related to) i and Y:M d／P = f( i, Y)The demand for real money balances is negatively related to the interest rate i,The demand for real money balances is positivelyrelated to the real income Y.Keynes’s model of the demand for mone y has the important implication that velocity is not constant but instead is positively related to interest rates, which fluctuate substantially. His theory also rejected the constancy of velocity because changes in people’s expectation about the normal le vel of interest rates would cause shifts in the demand for money that would cause velocity to shift as well. Thus Keynes’s liquidity preference theory casts doubt on classical quantity theory that nominal income is determined primarily by movements in the quantity of money.5. 凯恩斯理论的进一步发展(Further Developments in The Keynesian Approach)A. 交易需求(Transactions Demand)The conclusion of the Baumol–Tobin analysis is that the transactions component of money for demand is negatively related to the level of interest rates.The basic idea in the Baumol–Tobin analysis is that there is an opportunity cost of holdingmoney—the interest that can be earned on other assets. There is also a benefit to holding money—the avoidance of transaction costs. When interest rates increase, people will try to economize on the holding of money for transactions purpose because the opportunity cost of holding money has increased.B. 谨慎需求(Precautionary Demand)Model that explore the precautionary motive of the demand for money have been developed along lines similar to Baumol–Tobin framework. As interest rates rise, the opportunity cost of holding precautionary balances rises, and so the holdings of these money balances fall. The precautionary demand for money is negatively related to interest rates.C. 投机需求(Speculative Demand)Keynes’s analysis of the speculative demand for money was open to several serious criticisms. It indicated that an individual hold only money as a store of wealth when the expected return on bonds is less than the expected return on money and holdsonly bonds when the expected return on bonds is greater than the expected return on money. Solely in the rare instance when people have expected returns on bonds and money that are exactly equal would they hold both. Keynes’s analysis therefore implies that practically no one holds a diversified portfolio of bonds and money simultaneously as a store of wealth. Since diversification is apparently a sensible strategy of choosing which assets to hold, the fact that it rarely occurs in keynes’s analysis is a serious shortcoming of his theory of the speculative demand for money.Tobin developed a model of the speculative demand for money that attempted to avoid this criticism of keynes’s analysis. His basic idea was that not only do people care about the expected return on one assets versus another when they decide what to hold in their portfolio, but they also care about the riskiness of the returns from each asset. Tobin assumed that most people are risk-averse—that they would be willing to hold an asset with a lower expected return if it is less risky; An importantcharacteristic of money is that its return is certain; Tobin assumed it to zero. Bonds, by contrast, can have substantial fluctuations in price, and their returns can be quite risky and sometimes negative. So even if the expected returns on bonds exceed the expected return on money, people might still want to hold money as a store of wealth because it has less risk associated with its return than bonds do.The Tobin analysis also shows that people can reduce the total amount of risk in a portfolio by diversifying, that is, by holding both bonds and money. The model suggests that individual will hold bonds and money simultaneously as store of wealth. Since this is probably a more realistic description of people’s behavior than keynes’s, Tobin’s rationale for the speculative demand for money seems to rest on more solid ground.Tobin’s attempt to improve on keynes’s rationale for the speculative demand for money was only partly successful, however. It is still not clear that the speculative demand even exists. What if there are assets that have no risk—like money—but earn ahigher return? Will there be any speculative demand for money? No, because an individual will always be better off holding such an asset rather than money. The resulting portfolio will enjoy a higher expected return yet has no higher risk. Do such assets exist in the American economy? The answer is yes. U.S. Treasury bills, money market mutual fund shares, and other assets that have no default risk provide certain returns that are greater than those available on money. Therefore, why would anyone want to hold money balances as a store of wealth(ignoring for moment transactions and precautionary reason)?Although Tobin’s analysis did not explain why money is held as a store of wealth, it was an important development in our understanding of how people should choose among assets. Indeed, his analysis was an important step in the development of academic field of finance, which examines assets pricing and portfolio choice (decision to buy one asset over another).To sum up, further development of the Keynesian approach have attempted to give a more preciseexplanation for transaction, precautionary, and speculative demand for money. The attempt to improve Keynes’s rationale for the speculative demand for money has been only partly successful; it is still not clear that this demand even exist. However, the model of transactions and precautionary demand for money indicate that these components of money demand are negatively related to interest rates—suggesting that the velocity is not constant and that nominal income might be affected by factors other than the quantity of money—is still supported.6. 弗里德曼的现代货币数量论(Friedman’s Modern Quantity Theory Of Money)In 1956, Milton Friedman developed a theory of the demand for money in a famous article, ―The quantity Theory of Money: A Restatement.‖ Although Friedman frequently refers to Irving Fisher and the quantity theory, his analysis of demand for money is actually closer to that of Keynes and Cambridge economists than it is to Fisher.Like his predecessors, Friedman pursued the question of why people choose to hold money.Instead of analyzing the specific motives for holding money, as Keynes did, Friedman simply stated that the demand for money must be influenced by the same factors that influence the demand for any assets. Friedman then applied the theory of assets demand to money.The theory of asset demand (Chapter 5) indicates that the demand for money should be function of the resources available to individuals (their wealth) and the expected returns on other assets related to the expected return on money. Like Keynes, Friedman recognized that people want to hold a certain amount of real money balances (the quantity of money in real terms). From this reasoning, Friedman expressed his formulation of the demand for money as follows: M d／P＝f(Y p, r b－r m, r e－r m, πe－r m )where M d／P＝demand for real money balances Y p＝Friedman’s measure of wealth, known as permanent income(technically, the present discounted value of all expected future income, but more easily described as expected average long-run income)r m＝expected return on moneyr b＝expected return on bondsr e＝expected return on equity (common stocks)πe＝expected inflation rateOne implication of Friedman’s use of the concept of permanent income as a determinant of the demand for money is that the demand for money will not fluctuate much with business cycle movements.An individual can hold wealth in several forms besides money; Friedman categorized them into three types of assets: bonds, equity (common stocks), and goods. The incentives for holding these assets rather than money are represented by the expected return on each of these assets related to the expected return on money, the last three terms in the money demand function.The expected return on money rm, which appears in all three terms, is influenced by two factors:(1). The services provided by banks on deposits include in the money supply, such as provision of receipts in the form of canceled checks or automaticpaying of bills. When these services are increased, the expected return from holding money rises.(2). The interest payments on money balances. NOW accounts and other deposits that are included in the money supply current pay interest. As these interest payments rises, the return on money rises.The terms r b－r m and r e－r m represent the expected return on bonds and equity related to money; as they rise, the relative expected return on money falls, and the demand for money falls. The last term,πe－r m, represent the expected return on goods relative to money. The expected return from holding goods is the expected rate of capital gains that occurs when their prices rise and hence is equal to the expected inflation rateπe. If the expected inflation rate is 10%, for example, then goods’ prices are expected to rise at a 10% rate, and their expected return is 10%. Whenπe－r m rises, the expected return on goods relative to money rises, and the demand for money falls.7. 对弗里德曼理论和凯恩斯理论的区分(Distinguishing Between The Friedman and Keynesian Theories)A. 通过将许多资产视作货币的替代物，弗里德曼认为对于整体经济运行而言，具体的利率不止一种。