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 “loanable 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”本國居民購買的外國資產大于外國人購買的國內資產如果資本凈流出 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：一個人可以用一國通貨交換另一國通貨的比率我們用每一單位國內通貨可以兌換的外國通貨來表示匯率 在2008年7月16日的部分匯率 每單位美國美元可以兌換：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兩種標價方式：兩

7、種標價方式： “直接標價法直接標價法” 以一定數額外幣為標準，折為相應數額本幣表示匯率以一定數額外幣為標準，折為相應數額本幣表示匯率。絕大多數國家的貨幣采用直接標價法。絕大多數國家的貨幣采用直接標價法。 例如，人民幣對美元匯率為例如，人民幣對美元匯率為8.0 (￥)/1()。 “間接標價法間接標價法” 用一定數額本幣作為標準，折為相應數額外幣表示匯率用一定數額本幣作為標準，折為相應數額外幣表示匯率。世界上只有美元和英鎊采用間接標價法。世界上只有美元和英鎊采用間接標價法。 。30CHAPTER 5 The Open Economy升值與貶值升值與貶值升值升值（或者“堅挺”）： 按所能夠買到的外國

8、通貨量衡量的一國通貨的價值增加貶值貶值（或者“疲軟”）： 按所能夠買到的外國通貨量衡量的一國通貨的價值減少例如：2007年，美國美元 對歐元貶值9.5% 對韓元升值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量外幣，或者表示用比較少量本幣就能換得一定數量外幣，或者一定數量外幣只能換得較少數額本幣。升值使本國貨幣一定數量外幣只能換得較少數額本幣。升值使本國貨幣兌換價值提高，又稱本國貨幣變強了。兌換價值提高，又稱本國貨幣變強了。 本幣貶值本幣貶值 表示需要用較多數額本幣才能換得一定數量外幣，或表示需要用較多

9、數額本幣才能換得一定數量外幣，或者一定數量外幣能換得較多數額本幣。貶值使本國貨幣者一定數量外幣能換得較多數額本幣。貶值使本國貨幣兌換價值下降，因而本國貨幣變弱了。兌換價值下降，因而本國貨幣變弱了。32CHAPTER 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，本幣升值間接標價法間接標價法一定單位的外幣=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，本幣貶值直接標價法直接標價法實際匯率實際匯率實際匯率上升實際匯率下降本幣實際升值，國貨相對昂貴，競爭力下降本幣實際貶值，國貨相對便宜，競爭力上升PEPef33CHAPT

10、ER 5 The Open Economy均衡匯率的決定1.2E*=1.11.0歐元數量歐元數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（歐元的價格）美元/歐元Q*=1000億把自己看成是美國人，則匯率屬于直接標價法。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格。匯率（歐元價格）下降，對歐元（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通貨交換另一國通貨的比率，又稱之為名義匯率。34CHAPTER 5 The Open Economy美國人產生對歐元需求的原因有：對德國的產品和服務的偏好增加在德國投

11、資這導致“對歐元的需求線右移”。歐元升值升值。德國人產生對歐元供給的原因有：對美國的產品和服務的偏好增加在美國投資這導致對歐元的供給線右移，歐元貶值貶值。35CHAPTER 5 The Open Economy均衡匯率的波動歐元數量歐元數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圖示均衡匯率的變動圖示匯率美元/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真實匯率真實匯率真實匯率：真實匯率：一個人可以用一國物品與勞務交換另一國物品與勞務的比率真實匯率 =其中：P = 國內價格P* = 國外價格（用外國通貨衡量）e = 名義匯率，就是每一單位國內通貨可以兌換的外國通貨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巨無霸在美國的價格是$2.50，在日本的價格是400日元e = 120 日元/每美元e x P = 一個美國巨無霸的日元價格= (120 日元/每美元) x ($2.50 )= 300 日元/每個美國巨無霸計

15、算真實匯率：300 日元/每個美國巨無霸400 日元/每個日本巨無霸=e x PP*= 0.75 日本巨無霸/一個美國巨無霸42CHAPTER 5 The Open Economy真實匯率的解釋真實匯率的解釋“真實匯率 = 0.75 日本巨無霸/一個美國巨無霸”解釋：為在美國購買一個巨無霸，一個日本居民只需用在日本購買0.75個巨無霸的錢43CHAPTER 5 The Open Economye = 10 比索/每美元一杯星巴克拿鐵咖啡的價格： P = 3美元（美國），P* = 24 比索（墨西哥）A.用墨西哥比索表示一杯美國拿鐵咖啡的價格 B.計算真實匯率（一杯美國拿鐵咖啡可以購買多少墨西哥

16、拿鐵咖啡）4344CHAPTER 5 The Open Economy44e x P = （10 比索/每美元）x （3 美元/一杯美國拿鐵咖啡）= 30 比索/一杯美國拿鐵咖啡B.計算真實匯率30 比索/一杯美國拿鐵咖啡 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/一杯美國拿鐵咖啡e = 10 比索/每美元一杯星巴克拿鐵咖啡的價格： P = 3美元（美國），P* = 24 比索（墨西哥）A.用墨西哥比索表示一杯美國拿鐵咖啡的價格 45CHAPTER 5 The Open EconomyfE PeP.$EX X￥名義匯率直接標價法下：數值上升表示本幣（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 美國商品的價格（水平），上升表示單位美國商品越來越昂貴。這時，如果E、P不變，則單位美國商品能夠換得更多的中國商品，人民幣實際貶值。人民幣實際貶值。實際匯率：一單位（籃子）外國商品能夠換得多少單位（籃外國商品能夠換得多少單位（籃子）的本國商品子）的本國商品，數值上升表示本幣（人民幣）實際貶值實際貶值比如某商品（Thinkpad）在美國售價1000美元，在中國售價10000人民幣，如果名義匯率是6.6人民幣/美元，則美國商品折合人民幣為6600人民幣，一單位美國商品能夠換0.66（=6600/10000）中國商品。該數值

18、升高，表示一單位美國商品能換得更多的中國商品，人民幣實際貶值。該數值下降，表示一單位美國商品能換得的中國商品變少，人民幣實際升值。P中國商品的價格（水平），上升表示單位中國商品越來越昂貴。這時，如果E、Pf不變，則單位美國商品能夠換得的中國商品變少，人民幣實際升值。人民幣實際升值。46CHAPTER 5 The Open Economy有許多物品的真實匯率有許多物品的真實匯率P = 美國的物價水平，比如消費物價指數，衡量一 籃子物品的價格P* = 外國的物價水平真實匯率 = (e x P)/P* = 國內得到的一籃子物品相對于國外得到的一籃子物品的價格如果美國真實匯率上升，那美國物品相對于外國

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. 下列關于一個國家貿易赤字的表述中，哪個是不正確的？A.

38、出口 進口B. 資本凈流出 0C. 投資 儲蓄D. Y C + I + G 2. 一輛福特野馬SUV在美國的價格是24,000美元，在俄羅斯的價格是720,000盧布 如果購買力平價成立，名義匯率應該是多少（1美元兌換多少盧布）？7172CHAPTER 5 The Open Economy貿易赤字是說NX S. 721.下列關于一個國家貿易赤字的表述中，哪個是不正確的？ A. 出口 進口B.資本凈流出 0C.投資 儲蓄D.Y C + I + G 不正確！73CHAPTER 5 The Open Economy2.一輛福特野馬SUV在美國的價格是24,000美元，在俄羅斯的價格是720,000盧

39、布 如果購買力平價成立，名義匯率應該是多少（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