mankiw7e-chap05

1、S E V E N T H E D I T I O Naccounting identities for the open economythe small open economy modelwhat makes it “small”how the trade balance and exchange rate are determinedhow policies affect trade balance & exchange rateImports and exports (% of GDP), 2007ImportsExports3CHAPTER 5 The Open EconomyIn

2、 an open economy,spending need not equal outputsaving need not equal investment4CHAPTER 5 The Open EconomyThe national income identity in an open economyY = C + I + G + NXor, NX = Y (C + I + G )net exportsdomestic spendingoutput5CHAPTER 5 The Open EconomyTrade surpluses and deficitstrade surplus: ou

3、tput spending and exports imports Size of the trade surplus = NXtrade deficit: spending output and imports exports Size of the trade deficit = NXNX = EX IM = Y (C + I + G )6CHAPTER 5 The Open EconomyInternational capital flowsNet capital outflow=S I= net outflow of “loanable funds”= net purchases of

4、 foreign assets the countrys purchases of foreign assets minus foreign purchases of domestic assetsWhen S I, country is a net lenderWhen S I, country is a net borrower7CHAPTER 5 The Open EconomyThe link between trade & cap. flowsNX = Y (C + I + G )implies NX = (Y C G ) I = S Itrade balance = net cap

5、ital outflowThus, a country with a trade deficit (NX 0) is a net borrower (S 0，“资本流出”本国居民购买的外国资产大于外国人购买的国内资产如果资本净流出 0, S = 0,net capital outflow and NX fall by the amount I NX2NX1*rI 1I 2SI (r )227CHAPTER 5 The Open EconomyThe nominal exchange ratee = nominal exchange rate, the relative price of dom

6、estic currency in terms of foreign currency (e.g. Yen per Dollar)28CHAPTER 5 The Open Economy名义汇率名义汇率名义汇率：名义汇率：一个人可以用一国通货交换另一国通货的比率我们用每一单位国内通货可以兑换的外国通货来表示汇率 在2008年7月16日的部分汇率 每单位美国美元可以兑换：加拿大美元： 1.00欧元： 0.63日元： 104.77Mexican peso: 墨西哥 10.2529CHAPTER 5 The Open Economy两种标价方式：两种标价方式： “直接标价法直接标价法” 以一定数额外

7、币为标准，折为相应数额本币表示汇率以一定数额外币为标准，折为相应数额本币表示汇率。绝大多数国家的货币采用直接标价法。绝大多数国家的货币采用直接标价法。 例如，人民币对美元汇率为例如，人民币对美元汇率为8.0 (￥)/1()。 “间接标价法间接标价法” 用一定数额本币作为标准，折为相应数额外币表示汇率用一定数额本币作为标准，折为相应数额外币表示汇率。世界上只有美元和英镑采用间接标价法。世界上只有美元和英镑采用间接标价法。 。30CHAPTER 5 The Open Economy升值与贬值升值与贬值升值升值（或者“坚挺”）： 按所能够买到的外国通货量衡量的一国通货的价值增加贬值贬值（或者“疲软”

8、）： 按所能够买到的外国通货量衡量的一国通货的价值减少例如：2007年，美国美元 对欧元贬值9.5% 对韩元升值1.5% 31CHAPTER 5 The Open Economy汇率的升值与贬值： 本币升值本币升值 表示用比较少量本币就能换得一定数量外币，或者表示用比较少量本币就能换得一定数量外币，或者一定数量外币只能换得较少数额本币。升值使本国货币一定数量外币只能换得较少数额本币。升值使本国货币兑换价值提高，又称本国货币变强了。兑换价值提高，又称本国货币变强了。 本币贬值本币贬值 表示需要用较多数额本币才能换得一定数量外币，或表示需要用较多数额本币才能换得一定数量外币，或者一定数量外币能换得

9、较多数额本币。贬值使本国货币者一定数量外币能换得较多数额本币。贬值使本国货币兑换价值下降，因而本国货币变弱了。兑换价值下降，因而本国货币变弱了。32CHAPTER 5 The Open Economy一定单位的本币=若干单位的外币汇率上升 汇率下降外币升值，本币贬值外币贬值，本币升值间接标价法间接标价法一定单位的外币=若干单位的本币汇率上升 汇率下降外币贬值，本币升值外币升值，本币贬值直接标价法直接标价法实际汇率实际汇率实际汇率上升实际汇率下降本币实际升值，国货相对昂贵，竞争力下降本币实际贬值，国货相对便宜，竞争力上升PEPef33CHAPTER 5 The Open Economy均衡汇率的

10、决定1.2E*=1.11.0欧元数量欧元数量欧元的需求欧元的需求欧元的供给欧元的供给均衡汇率决定的图示均衡汇率决定的图示汇率（欧元的价格）美元/欧元Q*=1000亿把自己看成是美国人，则汇率属于直接标价法。把欧元（外汇）看作是一种普通商品，汇率就是用美元（本币）表示的这种商品的价格。汇率（欧元价格）下降，对欧元（外汇）的需求上升，欧元的供给减少，反之亦相反。这种均衡汇率反映了一国通货交换另一国通货的比率，又称之为名义汇率。34CHAPTER 5 The Open Economy美国人产生对欧元需求的原因有：对德国的产品和服务的偏好增加在德国投资这导致“对欧元的需求线右移”。欧元升值升值。德国人

11、产生对欧元供给的原因有：对美国的产品和服务的偏好增加在美国投资这导致对欧元的供给线右移，欧元贬值贬值。35CHAPTER 5 The Open Economy均衡汇率的波动欧元数量欧元数量欧元的需求欧元的需求欧元的供给欧元的供给均衡汇率的变动图示均衡汇率的变动图示汇率美元/欧元A few exchange rates, as of 6/24/2009countryexchange rateEuro area0.72 Euro/$Indonesia10,337 Rupiahs/$Japan95.9 Yen/$Mexico13.3 Pesos/$Russia31.4 Rubles

12、/$South Africa8.1 Rand/$U.K.0.61 Pounds/$37CHAPTER 5 The Open EconomyThe real exchange rate = real exchange rate, the relative price of domestic goods in terms of foreign goods (e.g. Japanese Big Macs per U.S. Big Mac)the lowercase Greek letter epsilon38CHAPTER 5 The Open EconomyUnderstanding the un

13、its of (Yen per $)($ per unit U.S. goods)Yen per unit Japanese goodsUnits of Japanese goods per unit of U.S. goodsYen per unit U.S. goodsYen per unit Japanese goods*ePP39CHAPTER 5 The Open Economy真实汇率真实汇率真实汇率：真实汇率：一个人可以用一国物品与劳务交换另一国物品与劳务的比率真实汇率 =其中：P = 国内价格P* = 国外价格（用外国通货衡量）e = 名义汇率，就是每一单位国内通货可以兑换的外

14、国通货e x PP*40CHAPTER 5 The Open Economyone good: Big Macprice in Japan: P* = 200 Yenprice in USA: P = $2.50nominal exchange rate e = 120 Yen/$To buy a U.S. Big Mac, someone from Japan would have to pay an amount that could buy 1.5 Japanese Big Macs.1202 501 5200 YenePP*$ . McZample 41CHAPTER 5 The Op

15、en Economy一种物品的例子一种物品的例子一个巨无霸在美国的价格是$2.50，在日本的价格是400日元e = 120 日元/每美元e x P = 一个美国巨无霸的日元价格= (120 日元/每美元) x ($2.50 )= 300 日元/每个美国巨无霸计算真实汇率：300 日元/每个美国巨无霸400 日元/每个日本巨无霸=e x PP*= 0.75 日本巨无霸/一个美国巨无霸42CHAPTER 5 The Open Economy真实汇率的解释真实汇率的解释“真实汇率 = 0.75 日本巨无霸/一个美国巨无霸”解释：为在美国购买一个巨无霸，一个日本居民只需用在日本购买0.75个巨无霸的钱

16、43CHAPTER 5 The Open Economye = 10 比索/每美元一杯星巴克拿铁咖啡的价格： P = 3美元（美国），P* = 24 比索（墨西哥）A.用墨西哥比索表示一杯美国拿铁咖啡的价格 B.计算真实汇率（一杯美国拿铁咖啡可以购买多少墨西哥拿铁咖啡）4344CHAPTER 5 The Open Economy44e x P = （10 比索/每美元）x （3 美元/一杯美国拿铁咖啡）= 30 比索/一杯美国拿铁咖啡B.计算真实汇率30 比索/一杯美国拿铁咖啡 24 比索/一杯墨西哥拿铁咖啡=e x PP*= 1.25杯墨西哥拿铁咖啡/一杯美国拿铁咖啡e = 10 比索/每美

17、元一杯星巴克拿铁咖啡的价格： P = 3美元（美国），P* = 24 比索（墨西哥）A.用墨西哥比索表示一杯美国拿铁咖啡的价格 45CHAPTER 5 The Open EconomyfE PeP.$EX X￥名义汇率直接标价法下：数值上升表示本币（人民币）名义贬值，比如从名义贬值，比如从6.6人民币/美元升至6.8人民币/美元fP 美国商品的价格（水平），上升表示单位美国商品越来越昂贵。这时，如果E、P不变，则单位美国商品能够换得更多的中国商品，人民币实际贬值。人民币实际贬值。实际汇率：一单位（篮子）外国商品能够换得多少单位（篮外国商品能够换得多少单位（篮子）的本国商品子）的本国商品，数值上

18、升表示本币（人民币）实际贬值实际贬值比如某商品（Thinkpad）在美国售价1000美元，在中国售价10000人民币，如果名义汇率是6.6人民币/美元，则美国商品折合人民币为6600人民币，一单位美国商品能够换0.66（=6600/10000）中国商品。该数值升高，表示一单位美国商品能换得更多的中国商品，人民币实际贬值。该数值下降，表示一单位美国商品能换得的中国商品变少，人民币实际升值。P中国商品的价格（水平），上升表示单位中国商品越来越昂贵。这时，如果E、Pf不变，则单位美国商品能够换得的中国商品变少，人民币实际升值。人民币实际升值。46CHAPTER 5 The Open Economy有

19、许多物品的真实汇率有许多物品的真实汇率P = 美国的物价水平，比如消费物价指数，衡量一 篮子物品的价格P* = 外国的物价水平真实汇率 = (e x P)/P* = 国内得到的一篮子物品相对于国外得到的一篮子物品的价格如果美国真实汇率上升，那美国物品相对于外国物品变得更昂贵 47CHAPTER 5 The Open Economy in the real world & our modelIn the real world:We can think of as the relative price of a basket of domestic goods in terms of a bask

20、et of foreign goodsIn our macro model:Theres just one good, “output.”So is the relative price of one countrys output in terms of the other countrys output48CHAPTER 5 The Open EconomyHow NX depends on U.S. goods become more expensive relative to foreign goods EX, IM NXU.S. net exports and the real ex

21、change rate, 1973-2009NX (% of GDP)Index (March 1973 = 100)020406080100120140-8%-6%-4%-2%0%2%4%197019751980198519901995200020052010Net exports(left scale)Trade-weighted real exchange rate index50CHAPTER 5 The Open EconomyThe net exports functionThe net exports function reflects this inverse relation

22、ship between NX and :NX = NX( )51CHAPTER 5 The Open EconomyThe NX curve for the U.S.0NXNX ()1When is relatively low, U.S. goods are relatively inexpensiveNX(1)so U.S. net exports will be high52CHAPTER 5 The Open EconomyThe NX curve for the U.S.0NXNX ()2At high enough values of , U.S. goods become so

23、 expensive that NX(2)we export less than we import53CHAPTER 5 The Open EconomyHow is determinedThe accounting identity says NX = S IWe saw earlier how S I is determined:S depends on domestic factors (output, fiscal policy variables, etc)I is determined by the world interest rate r *So, must adjust t

24、o ensure( )()*NX SI r54CHAPTER 5 The Open EconomyHow is determinedNeither S nor I depend on , so the net capital outflow curve is vertical. NXNX( )1( *)SI r adjusts to equate NX with net capital outflow, S I. 1NX 155CHAPTER 5 The Open EconomyInterpretation: supply and demand in the foreign exchange

25、marketdemand: Foreigners need dollars to buy U.S. net exports.NXNX( )1( *)SI rsupply: Net capital outflow (S I ) is the supply of dollars to be invested abroad. 1NX 156CHAPTER 5 The Open EconomyNext, four experiments:1. Fiscal policy at home2. Fiscal policy abroad3. An increase in investment demand(

26、exercise)4. Trade policy to restrict imports57CHAPTER 5 The Open Economy1. Fiscal policy at homeA fiscal expansion reduces national saving, net capital outflow, and the supply of dollars in the foreign exchange market causing the real exchange rate to rise and NX to fall.NXNX( )1( *)SI r 1NX 1NX 22(

27、 *)SI r 258CHAPTER 5 The Open Economy2. Fiscal policy abroadAn increase in r* reduces investment, increasing net capital outflow and the supply of dollars in the foreign exchange market causing the real exchange rate to fall and NX to rise.NXNX( )11(*)SI rNX 1 121()*SI r 2NX 2NOW YOU TRY: 3. Increas

28、e in investment demandNX( ) 111SINX 1NXDetermine the impact of an increase in investment demand on net exports, net capital outflow, and the real exchange rateANSWERS: 3. Increase in investment demandAn increase in investment reduces net capital outflow and the supply of dollars in the foreign excha

29、nge market NX( ) 111SINX 121SINX 2 2NXcausing the real exchange rate to rise and NX to fall.61CHAPTER 5 The Open Economy4. Trade policy to restrict importsNXNX ( )1SINX1 1NX ( )2At any given value of , an import quota IM NX demand for dollars shifts rightTrade policy doesnt affect S or I , so capita

30、l flows and the supply of dollars remain fixed. 262CHAPTER 5 The Open Economy4. Trade policy to restrict importsNXNX ( )1SINX1 1NX ( )2Results: 0 (demand increase) NX = 0(supply fixed) IM 0 (policy) EX 0(rise in ) 263CHAPTER 5 The Open EconomyThe determinants of the nominal exchange rateStart with t

31、he expression for the real exchange rate:*ePPSolve for the nominal exchange rate:*PeP64CHAPTER 5 The Open EconomyThe determinants of the nominal exchange rate( *,)ML rYP( )()*NX SI rSo e depends on the real exchange rate and the price levels at home and abroadand we know how each of them is determin

32、ed:*PeP*( *,)ML rYP65CHAPTER 5 The Open EconomyThe determinants of the nominal exchange rateRewrite this equation in growth rates (see “arithmetic tricks for working with percentage changes,” Chap 2 ):*PeP*ePPePP* For a given value of , the growth rate of e equals the difference between foreign and

33、domestic inflation rates. Inflation differentials and nominal exchange rates for a cross section of countries% change in nominal exchange rateinflation differentialIcelandMexicoU.K.S. KoreaJapanSingaporeCanadaAustraliaS. AfricaPakistan67CHAPTER 5 The Open EconomyPurchasing Power Parity (PPP)Two defi

34、nitions:A doctrine that states that goods must sell at the same (currency-adjusted) price in all countries.The nominal exchange rate adjusts to equalize the cost of a basket of goods across countries. Reasoning: arbitrage, the law of one price68CHAPTER 5 The Open EconomyPurchasing Power Parity (PPP)

35、PPP: e P = P* Cost of a basket of domestic goods, in foreign currency.Cost of a basket of domestic goods, in domestic currency.Cost of a basket of foreign goods, in foreign currency.Solve for e : e = P*/ P PPP implies that the nominal exchange rate between two countries equals the ratio of the count

36、ries price levels. 69CHAPTER 5 The Open EconomyDoes PPP hold in the real world?No, for two reasons:1.International arbitrage not possible. nontraded goods transportation costs2.Different countries goods not perfect substitutes.Nonetheless, PPP is a useful theory:Its simple & intuitiveIn the real wor

37、ld, nominal exchange rates tend toward their PPP values over the long run. no changeno change no changeno change 129.4-2.019.46.317.43.9115.1-0.32.2closed economysmall open economyactual changeNXIrSG T1980s1970sData: decade averages; all except r and are expressed as a percent of GDP; is

38、a trade-weighted index. CASE STUDY: The Reagan deficits revisited71CHAPTER 5 The Open Economy1. 下列关于一个国家贸易赤字的表述中，哪个是不正确的？A. 出口 进口B. 资本净流出 0C. 投资 储蓄D. Y C + I + G 2. 一辆福特野马SUV在美国的价格是24,000美元，在俄罗斯的价格是720,000卢布 如果购买力平价成立，名义汇率应该是多少（1美元兑换多少卢布）？7172CHAPTER 5 The Open Economy贸易赤字是说NX S. 721.下列关于一个国家贸易赤字的表述

39、中，哪个是不正确的？ A. 出口 进口B.资本净流出 0C.投资 储蓄D.Y C + I + G 不正确！73CHAPTER 5 The Open Economy2.一辆福特野马SUV在美国的价格是24,000美元，在俄罗斯的价格是720,000卢布 如果购买力平价成立，名义汇率应该是多少（1美元兑换多少卢布）？P* = 720,000 卢布P = 24,000 美元e = P*/P = 720000/24000 = 30 卢布/1美元7374CHAPTER 5 The Open EconomyThe U.S. as a large open economySo far, weve learn

40、ed long-run models for two extreme cases:closed economy (chap. 3)small open economy (chap. 5)A large open economy like the U.S. fallsbetween these two extremes. The results from large open economy analysis are a mixture of the results for the closed & small open economy cases. For example 75CHAPTER

41、5 The Open EconomyNXIrlarge open economysmall open economyclosed economyA fiscal expansion in three modelsfalls, but not as much as in small open economyfallsno changefalls, but not as much as in closed economynochangefallsrises, but not as much as in closed economynochangerisesA fiscal expansion causes national saving to fall.The effects of this depend on openness & size:Net exports-the difference between exports and importsa countrys output (Y ) and its spending (C + I