University of Warwick
Macroeconomics 1 (EC108)
Lecture 8
The Goods Market in an Open Economy
Lecturer: Natalie Chen
The Goods Market in an Open Economy
² The Relation in an Open Economy
² Equilibrium Output and the Trade Balance
– Increases in Demand – Domestic vs Foreign
– Depreciation, the Trade Balance, and Output
– Combining Exchange Rates and Fiscal Policies
² Looking at Dynamics: the -Curve
² Saving, Investment, and the Current Account Balance
The Goods Market in an Open Economy
² The US recession in 2009 led to a worldwide recession
² To understand what happened, we must expand the analysis and account
for openness in the analysis of goods markets
² This is what we now do
The IS Relation in the Open Economy
In an open economy, the demand for domestic goods is
= + ++ ¡
where , , and constitue the total domestic demand for goods, domestic
or foreign
Domestic demand
à ! 0 1
+ += ¡ + @ A +
(+) (+¡)
The IS Relation in the Open Economy
² Imports are positively related to domestic income and to the real ex-
change rate
0 1
= @ A
(++)
² Exports are positively related to foreign income ¤ and negatively related
to the real exchange rate
0 1
= @ ¤ A
(+¡)
The IS Relation in the Open Economy
The Demand for Domestic Goods and Net Exports (Blanchard, 2017)
² (a) The domestic demand for goods is an increasing function of income (output)
² Demand for domestic goods: subtract imports (b) and add exports (c)
² (d) The trade balance is a decreasing function of output
The IS Relation in the Open Economy
DD = C + I + G Domestic demand
AA = C + I + G ¡ M/ε Domestic demand for domestic goods
ZZ = C + I + G + X ¡ M/ε Demand for domestic goods
² AA is ‡atter than DD
² As long as some of the additional demand falls on domestic goods, AA
has a positive slope
² The distance between ZZ and AA is constant because exports do not
depend on domestic income but they depend on foreign income
Equilibrium Output and the Trade Balance
² The equilibrium condition for output can be expressed as
IM
Y = C (Y ¡ T ) + I (Y, r) + G + X (Y ¤, ε) ¡ (Y, ε)
ε
² Graphically, equilibrium output is at the point where demand equals out-
put, the intersection of ZZ and the 45-degree line
Equilibrium Output and the Trade Balance
Equilibrium Output and Net Exports (Blanchard, 2017)
The goods market is in equilibrium when domestic output is equal to the demand for domestic
goods. At the equilibrium level of output, the trade balance may show a de…cit or a surplus
Increases in Demand – Domestic vs Foreign
Di¤erences with a closed economy
² E¤ect on trade balance: an increase in output leads to a trade de…cit
² Smaller e¤ect of government spending on output: because ZZ is ‡atter
than DD, the multiplier is smaller in the open economy
Increases in Demand – Domestic vs Foreign
The E¤ects of an Increase in Government Spending (Blanchard, 2017)
An increase in government spending leads to an increase in output and to a trade de…cit
Increases in Demand – Domestic vs Foreign
The E¤ects of an Increase in Foreign Demand (Blanchard, 2017)
An increase in foreign demand leads to an increase in output and to a trade surplus
Increases in Demand – Domestic vs Foreign
² Summary
– An increase in domestic demand leads to an increase in domestic out-
put but leads also to a deterioration of the trade balance
– An increase in foreign demand leads to an increase in domestic output
and to an improvement in the trade balance
² Implications
– Shocks to demand in one country a¤ect all other countries
– Economic interactions complicate the task of policymakers. Policy
coordination is not so easy to achieve
Depreciation, the Trade Balance, and Output
² Recall the real exchange rate equation
=
¤
² And the de…nition of net exports
= ¡
² Therefore
= ( ¤ ) ¡ ( )
Depreciation, the Trade Balance, and Output
² A real depreciation a¤ects the trade balance through three channels
– Exports increase
– Imports decrease
– The relative price of foreign goods in terms of domestic goods 1
increases
² Marshall-Lerner condition: a real depreciation leads to an increase in
net exports
² A depreciation leads to a shift in demand, both foreign and domestic,
toward domestic goods. The shift in demand leads, in turn, to both an
increase in domestic output and an improvement in the trade balance
Marshall-Lerner Condition
² The Marshall-Lerner condition is the condition under which a real depre-
ciation (lower ) leads to an increase in net exports
² Consider the de…nition of net exports = ¡
² Assume that trade is initially balanced so that = 0 and = ,
or =
² Multiply both sides of = ¡ by to get
= ¡
Marshall-Lerner Condition
² Consider the e¤ect of a change in the real exchange rate ¢. Its e¤ect is
(¢) + (¢). If trade is initially balanced, = 0. Therefore
(¢) = (¢) + (¢) ¡ (¢)
² Divide both sides by to get
[ (¢)] = [(¢) ] + [ (¢)] ¡ [¢]
² If trade is initially balanced ( = ), then
(¢) = (¢) + (¢) ¡ ¢
Marshall-Lerner Condition
(¢) = (¢) + (¢) ¡ ¢
The change in the trade balance (as a ratio of exports) in response to a real
depreciation is equal to the sum of three terms
² The proportional change in the real exchange rate (negative for a real
depreciation)
² The proportional change in exports (positive for a real depreciation)
² The proportional change in imports (positive for a real depreciation)
If the Marshall-Lerner condition holds, the sum of the three terms is positive
(in which case a real depreciation improves the trade balance)
Combining Exchange Rates and Fiscal Policies
Reducing the Trade De…cit without Changing Output (Blanchard, 2017)
To reduce the trade de…cit without changing output, the government must both achieve a
depreciation and decrease government spending
Combining Exchange Rates and Fiscal Policies
If the government wants to eliminate the trade de…cit without changing output,
it must do two things
² Achieve a depreciation su¢cient to eliminate the trade de…cit
² Reduce government spending so as to shift ZZ back
The Disappearance of Current Account De…cits
in Euro Periphery Countries
Import compression: A decrease in imports (improved current account bal-
ance) triggered by a decrease in output
Euro Periphery Current Account De…cits since 2000 (Blanchard, 2017)
The Disappearance of Current Account De…cits
in Euro Periphery Countries
Greece’s real GDP, imports and exports all declined after 2008
Imports, Exports, and GDP in Greece since 2000 (Blanchard, 2017)
Looking at Dynamics: The J-Curve
² -curve: the adjustment process in the trade balance in response to a
real depreciation
² A depreciation initially increases the trade de…cit and, over time, exports
increase and imports decrease, reducing the trade de…cit
Looking at Dynamics: The J-Curve
The J-Curve (Blanchard, 2017)
A real depreciation leads initially to a deterioration and then to an improvement
of the trade balance
Looking at Dynamics: The J-Curve
The Real Exchange Rate and the Ratio of the Trade De…cit to GDP: US 1980–1990 (Blanchard,
2017)
The large real appreciation and subsequent real depreciation from 1980 to 1990
were mirrored, with a lag, by an increase and then a decrease in the trade de…cit
Saving, Investment, and Current Account Balance
² Recall
= + ++ ¡
² Therefore
¡ ¡ = +¡ + ¡
² Denote the current account by , so that the above equation becomes
= + ( ¡ ) +
so the current account balance is
= ¡ + ( ¡ )
Saving, Investment, and Current Account Balance
= ¡ + ( ¡ )
² An increase in investment must be re‡ected either by an increase in private
saving or public saving, or by a deterioration of the current account balance
² A deterioration in the government budget balance must be re‡ected by an
increase in either private saving, or by a decrease in investment, or else by
a deterioration of the current account balance
² A country with a high saving rate must have either a high investment rate
or a large current account surplus
