mankiw7e-chap05

1、S E V E N T H E D I T I O NIn this chapter, :accounting 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), 2007ImportsExports3CHAPTE

2、R 5 The Open EconomyIn 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 def

3、icitstrade surplus: output 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 “l(fā)oanable fu

4、nds”= net purchases of 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 =

5、S Itrade balance = net capital outflowThus, a country with a trade deficit (NX 0) is a net borrower (S 0，“資本流出”本國(guó)居民購(gòu)買的外國(guó)資產(chǎn)大于外國(guó)人購(gòu)買的國(guó)內(nèi)資產(chǎn)如果資本凈流出 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,

6、 the relative price of domestic currency in terms of foreign currency (e.g. Yen per Dollar)28CHAPTER 5 The Open Economy名義匯率名義匯率名義匯率：名義匯率：一個(gè)人可以用一國(guó)通貨交換另一國(guó)通貨的比率我們用每一單位國(guó)內(nèi)通貨可以兌換的外國(guó)通貨來(lái)表示匯率 在2008年7月16日的部分匯率 每單位美國(guó)美元可以兌換：加拿大美元： 1.00歐元： 0.63日元： 104.77Mexican peso: 墨西哥 10.2529CHAPTER 5 The Open Economy兩種標(biāo)價(jià)方式：兩

7、種標(biāo)價(jià)方式： “直接標(biāo)價(jià)法直接標(biāo)價(jià)法” 以一定數(shù)額外幣為標(biāo)準(zhǔn)，折為相應(yīng)數(shù)額本幣表示匯率以一定數(shù)額外幣為標(biāo)準(zhǔn)，折為相應(yīng)數(shù)額本幣表示匯率。絕大多數(shù)國(guó)家的貨幣采用直接標(biāo)價(jià)法。絕大多數(shù)國(guó)家的貨幣采用直接標(biāo)價(jià)法。 例如，人民幣對(duì)美元匯率為例如，人民幣對(duì)美元匯率為8.0 (￥)/1()。 “間接標(biāo)價(jià)法間接標(biāo)價(jià)法” 用一定數(shù)額本幣作為標(biāo)準(zhǔn)，折為相應(yīng)數(shù)額外幣表示匯率用一定數(shù)額本幣作為標(biāo)準(zhǔn)，折為相應(yīng)數(shù)額外幣表示匯率。世界上只有美元和英鎊采用間接標(biāo)價(jià)法。世界上只有美元和英鎊采用間接標(biāo)價(jià)法。 。30CHAPTER 5 The Open Economy升值與貶值升值與貶值升值升值（或者“堅(jiān)挺”）： 按所能夠買到的外國(guó)

8、通貨量衡量的一國(guó)通貨的價(jià)值增加貶值貶值（或者“疲軟”）： 按所能夠買到的外國(guó)通貨量衡量的一國(guó)通貨的價(jià)值減少例如：2007年，美國(guó)美元 對(duì)歐元貶值9.5% 對(duì)韓元升值1.5% 31CHAPTER 5 The Open Economy匯率的升值與貶值： 本幣升值本幣升值 表示用比較少量本幣就能換得一定數(shù)量外幣，或者表示用比較少量本幣就能換得一定數(shù)量外幣，或者一定數(shù)量外幣只能換得較少數(shù)額本幣。升值使本國(guó)貨幣一定數(shù)量外幣只能換得較少數(shù)額本幣。升值使本國(guó)貨幣兌換價(jià)值提高，又稱本國(guó)貨幣變強(qiáng)了。兌換價(jià)值提高，又稱本國(guó)貨幣變強(qiáng)了。 本幣貶值本幣貶值 表示需要用較多數(shù)額本幣才能換得一定數(shù)量外幣，或表示需要用較多

9、數(shù)額本幣才能換得一定數(shù)量外幣，或者一定數(shù)量外幣能換得較多數(shù)額本幣。貶值使本國(guó)貨幣者一定數(shù)量外幣能換得較多數(shù)額本幣。貶值使本國(guó)貨幣兌換價(jià)值下降，因而本國(guó)貨幣變?nèi)趿恕稉Q價(jià)值下降，因而本國(guó)貨幣變?nèi)趿恕?2CHAPTER 5 The Open Economy一定單位的本幣=若干單位的外幣匯率上升 匯率下降外幣升值，本幣貶值外幣貶值，本幣升值間接標(biāo)價(jià)法間接標(biāo)價(jià)法一定單位的外幣=若干單位的本幣匯率上升 匯率下降外幣貶值，本幣升值外幣升值，本幣貶值直接標(biāo)價(jià)法直接標(biāo)價(jià)法實(shí)際匯率實(shí)際匯率實(shí)際匯率上升實(shí)際匯率下降本幣實(shí)際升值，國(guó)貨相對(duì)昂貴，競(jìng)爭(zhēng)力下降本幣實(shí)際貶值，國(guó)貨相對(duì)便宜，競(jìng)爭(zhēng)力上升PEPef33CHAPT

10、ER 5 The Open Economy均衡匯率的決定1.2E*=1.11.0歐元數(shù)量歐元數(shù)量歐元的需求歐元的需求歐元的供給歐元的供給均衡匯率決定的圖示均衡匯率決定的圖示匯率（歐元的價(jià)格）美元/歐元Q*=1000億把自己看成是美國(guó)人，則匯率屬于直接標(biāo)價(jià)法。把歐元（外匯）看作是一種普通商品，匯率就是用美元（本幣）表示的這種商品的價(jià)格。匯率（歐元價(jià)格）下降，對(duì)歐元（外匯）的需求上升，歐元的供給減少，反之亦相反。這種均衡匯率反映了一國(guó)通貨交換另一國(guó)通貨的比率，又稱之為名義匯率。34CHAPTER 5 The Open Economy美國(guó)人產(chǎn)生對(duì)歐元需求的原因有：對(duì)德國(guó)的產(chǎn)品和服務(wù)的偏好增加在德國(guó)投

11、資這導(dǎo)致“對(duì)歐元的需求線右移”。歐元升值升值。德國(guó)人產(chǎn)生對(duì)歐元供給的原因有：對(duì)美國(guó)的產(chǎn)品和服務(wù)的偏好增加在美國(guó)投資這導(dǎo)致對(duì)歐元的供給線右移，歐元貶值貶值。35CHAPTER 5 The Open Economy均衡匯率的波動(dòng)歐元數(shù)量歐元數(shù)量歐元的需求歐元的需求歐元的供給歐元的供給均衡匯率的變動(dòng)圖示均衡匯率的變動(dòng)圖示匯率美元/歐元A few exchange rates, as of 6/24/200937CHAPTER 5 The Open EconomyThe real exchange rate = real exchange rate, the relative pri

12、ce 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 units 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

13、. goodsYen per unit Japanese goods*ePP39CHAPTER 5 The Open Economy真實(shí)匯率真實(shí)匯率真實(shí)匯率：真實(shí)匯率：一個(gè)人可以用一國(guó)物品與勞務(wù)交換另一國(guó)物品與勞務(wù)的比率真實(shí)匯率 =其中：P = 國(guó)內(nèi)價(jià)格P* = 國(guó)外價(jià)格（用外國(guó)通貨衡量）e = 名義匯率，就是每一單位國(guó)內(nèi)通貨可以兌換的外國(guó)通貨e x PP*40CHAPTER 5 The Open Economyone good: Big Macprice in Japan: P* = 200 Yenprice in USA: P = $2.50nominal exchange rate e

14、= 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 Open Economy一種物品的例子一種物品的例子一個(gè)巨無(wú)霸在美國(guó)的價(jià)格是$2.50，在日本的價(jià)格是400日元e = 120 日元/每美元e x P = 一個(gè)美國(guó)巨無(wú)霸的日元價(jià)格= (120 日元/每美元) x ($2.50 )= 300 日元/每個(gè)美國(guó)巨無(wú)霸計(jì)

15、算真實(shí)匯率：300 日元/每個(gè)美國(guó)巨無(wú)霸400 日元/每個(gè)日本巨無(wú)霸=e x PP*= 0.75 日本巨無(wú)霸/一個(gè)美國(guó)巨無(wú)霸42CHAPTER 5 The Open Economy真實(shí)匯率的解釋真實(shí)匯率的解釋“真實(shí)匯率 = 0.75 日本巨無(wú)霸/一個(gè)美國(guó)巨無(wú)霸”解釋：為在美國(guó)購(gòu)買一個(gè)巨無(wú)霸，一個(gè)日本居民只需用在日本購(gòu)買0.75個(gè)巨無(wú)霸的錢43CHAPTER 5 The Open Economye = 10 比索/每美元一杯星巴克拿鐵咖啡的價(jià)格： P = 3美元（美國(guó)），P* = 24 比索（墨西哥）A.用墨西哥比索表示一杯美國(guó)拿鐵咖啡的價(jià)格 B.計(jì)算真實(shí)匯率（一杯美國(guó)拿鐵咖啡可以購(gòu)買多少墨西哥

16、拿鐵咖啡）4344CHAPTER 5 The Open Economy44e x P = （10 比索/每美元）x （3 美元/一杯美國(guó)拿鐵咖啡）= 30 比索/一杯美國(guó)拿鐵咖啡B.計(jì)算真實(shí)匯率30 比索/一杯美國(guó)拿鐵咖啡 24 比索/一杯墨西哥拿鐵咖啡=e x PP*= 1.25杯墨西哥拿鐵咖啡/一杯美國(guó)拿鐵咖啡e = 10 比索/每美元一杯星巴克拿鐵咖啡的價(jià)格： P = 3美元（美國(guó)），P* = 24 比索（墨西哥）A.用墨西哥比索表示一杯美國(guó)拿鐵咖啡的價(jià)格 45CHAPTER 5 The Open EconomyfE PeP.$EX X￥名義匯率直接標(biāo)價(jià)法下：數(shù)值上升表示本幣（人民幣）名

17、義貶值，比如從名義貶值，比如從6.6人民幣/美元升至6.8人民幣/美元fP 美國(guó)商品的價(jià)格（水平），上升表示單位美國(guó)商品越來(lái)越昂貴。這時(shí)，如果E、P不變，則單位美國(guó)商品能夠換得更多的中國(guó)商品，人民幣實(shí)際貶值。人民幣實(shí)際貶值。實(shí)際匯率：一單位（籃子）外國(guó)商品能夠換得多少單位（籃外國(guó)商品能夠換得多少單位（籃子）的本國(guó)商品子）的本國(guó)商品，數(shù)值上升表示本幣（人民幣）實(shí)際貶值實(shí)際貶值比如某商品（Thinkpad）在美國(guó)售價(jià)1000美元，在中國(guó)售價(jià)10000人民幣，如果名義匯率是6.6人民幣/美元，則美國(guó)商品折合人民幣為6600人民幣，一單位美國(guó)商品能夠換0.66（=6600/10000）中國(guó)商品。該數(shù)值

18、升高，表示一單位美國(guó)商品能換得更多的中國(guó)商品，人民幣實(shí)際貶值。該數(shù)值下降，表示一單位美國(guó)商品能換得的中國(guó)商品變少，人民幣實(shí)際升值。P中國(guó)商品的價(jià)格（水平），上升表示單位中國(guó)商品越來(lái)越昂貴。這時(shí)，如果E、Pf不變，則單位美國(guó)商品能夠換得的中國(guó)商品變少，人民幣實(shí)際升值。人民幣實(shí)際升值。46CHAPTER 5 The Open Economy有許多物品的真實(shí)匯率有許多物品的真實(shí)匯率P = 美國(guó)的物價(jià)水平，比如消費(fèi)物價(jià)指數(shù)，衡量一 籃子物品的價(jià)格P* = 外國(guó)的物價(jià)水平真實(shí)匯率 = (e x P)/P* = 國(guó)內(nèi)得到的一籃子物品相對(duì)于國(guó)外得到的一籃子物品的價(jià)格如果美國(guó)真實(shí)匯率上升，那美國(guó)物品相對(duì)于外國(guó)

19、物品變得更昂貴 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 basket of foreign goodsIn our macro model:Theres just one good, “output.”So is the relative price of one countrys output in terms

20、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 exchange rate, 1973-2009NX (% of GDP)Index (March 1973 = 100)020406080100120140-8%-6%-4%-2%0%2%4%1970197519801985199019952000200

21、52010Net exports(left scale)Trade-weighted real exchange rate index50CHAPTER 5 The Open EconomyThe net exports functionThe net exports function reflects this inverse relationship between NX and :NX = NX( )51CHAPTER 5 The Open EconomyThe NX curve for the U.S.0NXNX ()1When is relatively low, U.S. good

22、s 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 expensive that NX(2)we export less than we import53CHAPTER 5 The Open EconomyHow is determinedThe accounting identity says NX

23、 = 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 to ensure( )()*NX SI r54CHAPTER 5 The Open EconomyHow is determinedNeither S nor I depend on , so the net capital outflow curve

24、 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 marketdemand: Foreigners need dollars to buy U.S. net exports.NXNX( )1( *)SI rsupply: Net capital outflow (S I ) is the supply

25、 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(exercise)4. Trade policy to restrict imports57CHAPTER 5 The Open Economy1. Fiscal policy at homeA fiscal expansion reduces nat

26、ional 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( *)SI r 258CHAPTER 5 The Open Economy2. Fiscal policy abroadAn increase in r* reduces investment, increasing net capital outfl

27、ow 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. Increase in investment demandNX( ) 111SINX 1NXDetermine the impact of an increase in investment demand on net exports, net capital ou

28、tflow, 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 exchange market NX( ) 111SINX 121SINX 2 2NXcausing the real exchange rate to rise and NX to fall.61CHAPTER 5 The Open Economy4. Tra

29、de 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 capital flows and the supply of dollars remain fixed. 262CHAPTER 5 The Open Economy4. Trade policy to restrict importsNXNX ( )1SINX1

30、 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 the expression for the real exchange rate:*ePPSolve for the nominal exchange rate:*PeP64CHAPTER 5 The Open EconomyThe determina

31、nts 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 determined:*PeP*( *,)ML rYP65CHAPTER 5 The Open EconomyThe determinants of the nominal exchange rateRewrite this equation in growth ra

32、tes (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 domestic inflation rates. Inflation differentials and nominal exchange rates for a cross section of countries% change in nomin

33、al exchange rateinflation differentialIcelandMexicoU.K.S. KoreaJapanSingaporeCanadaAustraliaS. AfricaPakistan67CHAPTER 5 The Open EconomyPurchasing Power Parity (PPP)Two definitions:A doctrine that states that goods must sell at the same (currency-adjusted) price in all countries.The nominal exchang

34、e 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)PPP: e P = P* Cost of a basket of domestic goods, in foreign currency.Cost of a basket of domestic goods, in domestic currency

35、.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 countries price levels. 69CHAPTER 5 The Open EconomyDoes PPP hold in the real world?No, for two reasons:1.International arbitrage n

36、ot possible.nontraded goodstransportation costs2.Different countries goods not perfect substitutes.Nonetheless, PPP is a useful theory:Its simple & intuitiveIn the real world, nominal exchange rates tend toward their PPP values over the long run. no changeno change no changeno change 129.4-2.019

37、.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 a trade-weighted index. CASE STUDY: The Reagan deficits revisited71CHAPTER 5 The Open Economy1. 下列關(guān)于一個(gè)國(guó)家貿(mào)易赤字的表述中，哪個(gè)是不正確的？A.

38、出口 進(jìn)口B. 資本凈流出 0C. 投資 儲(chǔ)蓄D. Y C + I + G 2. 一輛福特野馬SUV在美國(guó)的價(jià)格是24,000美元，在俄羅斯的價(jià)格是720,000盧布 如果購(gòu)買力平價(jià)成立，名義匯率應(yīng)該是多少（1美元兌換多少盧布）？7172CHAPTER 5 The Open Economy貿(mào)易赤字是說(shuō)NX S. 721.下列關(guān)于一個(gè)國(guó)家貿(mào)易赤字的表述中，哪個(gè)是不正確的？ A. 出口 進(jìn)口B.資本凈流出 0C.投資 儲(chǔ)蓄D.Y C + I + G 不正確！73CHAPTER 5 The Open Economy2.一輛福特野馬SUV在美國(guó)的價(jià)格是24,000美元，在俄羅斯的價(jià)格是720,000盧

39、布 如果購(gòu)買力平價(jià)成立，名義匯率應(yīng)該是多少（1美元兌換多少盧布）？P* = 720,000 盧布P = 24,000 美元e = P*/P = 720000/24000 = 30 盧布/1美元7374CHAPTER 5 The Open EconomyThe U.S. as a large open economySo far, weve learned long-run models for two extreme cases:closed economy (chap. 3)small open economy (chap. 5)A large open economy like the U

40、.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 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 economynocha