Download open economy 開放的經濟體系

Part 11
THE MACROECONOMICS OF
OPEN ECONOMIES
Open and Closed Economies
•
A closed economy 封閉的經濟體系：
one that does not interact with other economies:
no exports, no imports, no capital flows.
•
An open economy 開放的經濟體系：
one that interacts with other economies around the
world.
1. buys/ sells goods & services in world product
markets: International flow of goods.
2. buys/ sells capital assets in world financial markets:
International flow of financial resources.
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1. The International Flow of Goods
• Exports (EX，出口)：goods & services
produced domestically and sold abroad.
• Imports (IM，進口)：goods and services
produced abroad and sold domestically.
• Net exports (NX，淨出口)
or trade balance (TB，貿易淨額)：
NX=EX-IM
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The Flow of Goods
Net exports or Trade balance：
(1) NX=0，EX=IM：balanced trade 貿易平衡
(2) NX > 0，EX > IM：trade surplus 貿易盈餘
(出超)
(3) NX < 0，EX < IM：trade deficit 貿易赤字
（入超）
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Factors that Affect NX
(1) Tastes of consumers for domestic & foreign
goods.
(2) The incomes of consumers at home and abroad.
(3) The prices of goods at home (P) and abroad (PF).
(4) The exchange rates (匯率，e) at which people can
use domestic currency to buy foreign currencies.
(5) The costs of transporting goods from country to
country.
(6) The policies of the government toward
international trade.
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Taiwan data: NX=EX-IM
Fig31.1
出口與進口佔GDP比例（%）
80
70
60
%
50
出口比例
40
進口比例
30
20
10
0
1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005
年度
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2. The Flow of Financial Resources
• Net capital outflow (NCO)，淨資本流出：
purchase of foreign assets by domestic residents
minus purchase of domestic assets by foreigners.
• A Taiwanese buys stock in the US corporation
 Capital outflow （$流出）
• a US citizen buys Taiwan stock.
 Capital inflow （$流入）
Net capital outflow =capital outflow –capital inflow
（$淨流出）
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Factors that Influence NCO
(1) real interest rates (rF) being paid on foreign assets.
real interest rates ( r ) being paid on domestic assets.
 the differences ( r- rF ) matters
As r↑ relative to rF
 less capital outflow and more capital inflow
NCO↓
(2) The perceived economic and political risks of
holding assets abroad.
(3) The government policies that affect foreign
ownership of domestic assets.
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Saving, Investment, and
the International Flows
• Expenditure approach of GDP:
Y = C + I + G + NX
• Income approach of GDP:
S= Y-C-G
→ S =Y-C-G = I + NX (Ch26 Identity)
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Saving, Investment, and
the International Flows
• Saving S = △wealth
(wealth: deposits/bonds/stocks/houses)
= △domestic assets + △foreign assets
= domestic investment +net capital outflow
= I + NCO
• An economy’s saving can be used to either
finance investment at home or to buy assets
abroad .
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The Equality of NX and NCO
• National saving (S):
S = I + NX or S= I + NCO
NX = NCO
補充：
國際收支帳＝經常帳＋資本帳（小）＋金融帳
經常帳 ：包含NX
金融帳 ：包含這裡的NCO
 Ch31 and Ch32:簡化分析
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Taiwan data: S-I=NX
Fig 31.2a
國民儲蓄與投資比例
45
40
35
30
25
%
國民儲蓄比例
投資比例
20
15
10
5
0
1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005
年度
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Taiwan data: NCO=NX
Fig 31.2b
NCO比例(%)
25
20
15
%
10
NCO比例
5
0
1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005
-5
-10
年度
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The Prices for International Transactions:
Real and Nominal Exchange Rates
• International transactions are influenced by
international prices.
• The nominal exchange rate 名目匯率 ：
the rate at which a person can trade the
currency of one country for the currency of
another.
貨幣的價格（以另一種貨幣表示 ）
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Nominal Exchange Rates
• The nominal exchange rate （e）
is expressed in two ways:
(1) in units of foreign currency per one Taiwan dollar.
(2) in units of Taiwan dollars per one unit of the
foreign currency.
• Assume the exchange rate between the NT$ and
U.S. dollar is NT$30.3 to one U.S.dollar.
(1) NT$1 trades for 1/30.3 (= 0.033) of a U.S. dollar.
(2) One U.S. dollar trades for NT$30.3 採用
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Nominal Exchange Rates
• Appreciation 升值:
an increase in the value of a currency
as measured by the amount of foreign currency
it can buy.
• Depreciation 貶值: a decrease
eg,
(1)US$1=NT$33  NT$30
（美金貶值）
NT$1=US$(1/33)  US$(1/30)：台幣升值
(2) US$1=NT$33  NT$35：台幣貶值(美金升值)
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Taiwan data: 台幣對美金匯率
台幣對美金匯率（1960-2007年資料）
45
40
35
25
20
15
10
5
年度
05
20
02
20
99
19
96
19
93
19
90
19
87
19
84
19
81
19
78
19
75
19
72
19
69
19
66
19
63
19
60
0
19
美金匯率
30
美金匯率
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匯率換算
2008/4/23
US$1=日圓$103
US$1=NT$30.3
日圓$103=US$1=NT$30.3
日圓$1=NT$0.29
(NT$1=日圓$3.4 )
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Real Exchange Rates
The real exchange rate 實質匯率:
the rate at which a person can trade the goods and
services of one country for the goods and services of
another.
PX
Y

X
PY
X  Q : domestic goods
Y  QF : foreign goods
• The real exchange rate
compares the prices of
domestic goods and
foreign goods in the
domestic economy.
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Real Exchange Rates
• The real exchange rate depends on
the nominal exchange rate and the prices of goods in
the two countries measured in local currencies.
Real exchange rate
QF
foreign goods


domestic goods
Q
Domestic price

Foreign price  Nominal exchange rate
P

ePF
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Real Exchange Rates
• If a case of Taiwan beer is NT$30,
a case of American beer is US$0.5,
and e =30,
QF
P
30



2
Q ePF 30*0.5
P  2(ePF ) or QF  2Q
A case of Taiwan beer is twice as expensive as American beer.
Or the real exchange rate is 2 cases of American beer per case
of Taiwan beer.
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Real Exchange Rates
• The real exchange rate is a key determinant of
how much a country exports and imports.
(real exchange rate = terms of trade 貿易條件)
• A depreciation (fall) in Taiwan real exchange rate:
貶值 (P/ePF) ↓ ，due to P ↓or PF↑ or e↑
 Taiwan goods have become cheaper relative to
foreign goods.
IM ↓ and EX ↑
NX ↑
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A First Theory of Exchange -Rate Determination:
Purchasing -Power Parity
• The simplest and most widely accepted theory
explaining the variation of currency exchange rates.
• Purchasing-Power Parity Theory
（PPP theory）購買力平價說：
a unit of any given currency should be able to
buy the same quantity of goods in all countries
(same purchasing power).
LR equilibrium theory
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Logic of PPP
NT$1
= able to buy the same quantity of goods in all
countries.
=(1/P) unit of goods in Taiwan
=(1/e)/PF unit of goods in foreign country
 1/P= 1/ePF  P/ePF =1
real exchange rate  
QF
P

1
Q e * PF
P  (e * PF ) or QF  Q
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Logic of PPP
• PPP based on the law of one price.
（競爭）整合市場的單一價格
• According to the law of one price, a good must sell
for the same price in all locations.
• If the law of one price were not true, unexploited
profit opportunities would exist.
 arbitrage.套利：the process of taking advantage
of differences in prices in different markets.
 eventually prices that differed in two markets
would necessarily converge. 收斂
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Arbitrage 1
• If real exchange rate = P/ePF <1
P < ePF
Arbitrage 1：
P < ePF _ EX↑, IM↓
demand for domestic goods↑& demand for foreign goods↓
Possible that P↑ or PF ↓,
so that P=ePF, NX=0
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Arbitrage 2
• If real exchange rate = P/ePF <1
P<ePF  NX>0  demand for NT$↑(Ch32)
 e*↓(升值)
(1) 若未升值(預期升值)，則
熱錢流入(Arbitrage): buy NT$ and sell it later.
US$1  NT$33  US$ (33/28) = US$1.18
(2) As demand for NT$↑, the value of NT$↑  e*↓
• 民74年以前，1美元兌換新台幣36-40元左右。由於國際美
元走弱及中美貿易逆差擴大，美國開始壓迫我國新台幣升
值，中央銀行採緩慢升值方式，因而導致國外熱錢大量流
入國內。78年元月，新台幣收盤價為28元兌1美元。
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Implications of PPP
• According to PPP, P/ePF =1
 Exchange rates move to ensure that in the LR.
（LR equilibrium exchange rate: e*）
• P/ePF =1  e* = P/PF
e* must reflect the different price levels in two countries.
eg, P=NT$100, PF =US$3.3
e* = P/PF =NT$100/US$3.3= NT$30/US$
(美金3.3元的東西需花台幣100元，即台幣只值美金的1/30)
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Implications of PPP
LR: P depends on Ms ；PF depends on MFs
△e*
例如： M↑ P↑
依據PPP ( e* = P/PF) …  e*↑（貶值）
When CB prints large quantities of money,
the money loses value both
in terms of goods it can buy and
in terms of the amount of other currencies it can
buy.
 the currency depreciates relative to other currencies.
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Implications of PPP
• 補充PPP較鬆的條件：1改為常數
• real exchange rate = P/ePF = c
P  e  PF
  e  P  PF
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Figure 31.3 Money, Prices, and the Nominal
Exchange Rate During the German Hyperinflation
Indexes
(Jan. 1921 5 100)
1,000,000,000,000,000
Money supply
10,000,000,000
Price level
100,000
1
Exchange rate
.00001
.0000000001
1921
1922
1923
1924
1925
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Limitations of PPP
(1) Many goods are not easily traded or shipped
from one country to another.
 Nontraded goods：非貿易財
(2) Tradable goods are not always perfect
substitutes when they are produced in different
countries.
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Summary
Y  C  I  G  NX
S  Y  C  G  I  NX
S  I  NCO
NX  NCO
nominal exchange rate (e)
QF
P
real exchange rate 

Q ePF
PPP theory: LR equilibrium
QF
P
real exchange rate 

1
Q e * PF
P
or e* 
PF
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