The Marshall-Lerner Condition, the J-curve, and the US trade deficit
Read the following article before reading the blog post below:
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In IB Economics we’ve been studying concepts relating to balance of trade and exchange rates. The Marshall-Lerner Condition and the J-curve are two concepts that explain the relationship between a the exchange rate for a nation’s currency and the country’s balance of trade. (click on the graph to see a larger version)
Common sense might indicate that if a country’s currency (let’s say the US dollar) depreciates relative to other currencies, then this should lead to an improvement in the country’s balance of trade (economists call this the current account ). The reasoning goes as such: a weaker dollar means foreigners will have to give up less of their money in order to get one dollar’s worth of American output. At the same time, since the dollar is worth less in foreign currency, imports become more expensive, as Americans have to fork over more dollars for a certain amount of another country’s output; hence, imports should decrease.
Fewer imports and more exports means an improvement in the country’s balance of trade, right? Well, not necessarily. What matters is not whether a country is importing less and exporting more, rather, whether the increase in income from exports exceeds the decrease in expenditures on imports. Here is where the Marshall-Lerner Condition can be applied.
The M-L condition examines the price elasticities of demand for exports and imports of a particular country. Say the US experiences a depreciation of its currency (as it has over the last year or so). If foreigners’ demand for exports from America is relatively elastic, then a slightly weaker dollar should cause a dramatic increase in foreign demand for American output, causing export income in the US to rise dramatically. On the other hand, if American’s demand for imports is highly price elastic, then a slightly weaker dollar should likewise cause Americans’ demand for imports to decrease drastically, reducing greatly American’s expenditures on imports. If the combined elasticities of demand for exports and imports is elastic (i.e. the coefficient is greater than 1), then a depreciation of a nations currency will shift its current account towards surplus. This is the Marshall-Lerner Condition.
Marshall-Lerner Condition: If PEDx + PEDm > 1. then a depreciation or a devaluation of a nation’s currency will shift the the balance on its current account towards surplus.
So what if the Marshall Lerner Condition is not met? Demand for exports and imports may not always be so responsive to changes in exchange rates. Imagine a scenario where a weaker dollar does little to change foreign demand for America’s output. In this case income from exports may actually decline (in real terms, since the dollar is weaker) as the dollar depreciates. Likewise, if Americans’ demand for imports is highly inelastic, then more expensive imports will only minimally affect Americans’ demand for imported goods. in which case expenditures on imports may actually rise as they become more expensive. In this case,
where the elasticities of demand for exports and imports are highly inelastic, a depreciation of the currency will actually worsen a trade deficit. Americans’ import expenditures will go up while export income from abroad will decline shifting the current account further into deficit.
In the article above. some data is presented that points to evidence that in the US today, the Marshall-Lerner Condition is in fact being met:
“Exports in the year through September are up by 12 percent from 2006, while the dollar’s trade-weighted exchange rate dropped by only 6 percent. That means foreigners may actually be spending more – even in their own currencies – on American products. It’s a support that the American economy, and in turn the global economy, can really use right now.
Of course, this process isn’t helping the trade deficit too much, No one, it seems, can change Americans’ taste for foreign products. But it does show, for all to see, that the risks of an open economy are at least somewhat balanced by the benefits.”
An increase in exports of 12% in response to a 6% weakening of the dollar indicates a price elasticity of demand coefficient for America’s exports of 2, meaning foreigners are highly responsive to cheaper US goods.
We can assume that Americans’ demand for imports is highly inelastic, as the article hints at when it says, “imports to the United States, including oil, are still rising in volume and value.” If a 6% weaker dollar leads to an increase in expenditures on imports, then demand must be less than one. In order for M-L Condition to be met, PEDx+PEDm must be greater than 1. Clearly, with a PEDx of 2, the condition is met, and a weaker dollar in leading to an improvement in America’s balance of trade with the rest of the world.
- What is the J-curve effect? Based on the evidence from the article, where on the J-curve is the US right now?
- Is America experiencing an improvement in or a worsening of its current account deficit ?
- What determinants of demand are fueling America’s ever-increasing expenditures on imports?
- What should happen to the elasticity of demand for imports if the dollar remains weak in the long-run? How will this affect America’s position on the J-curve?
About the author: Jason Welker teaches International Baccalaureate and Advanced Placement Economics at Zurich International School in Switzerland. In addition to publishing various online resources for economics students and teachers, Jason developed the online version of the Economics course for the IB and is has authored two Economics textbooks: Pearson Baccalaureate’s Economics for the IB Diploma and REA’s AP Macroeconomics Crash Course. Jason is a native of the Pacific Northwest of the United States, and is a passionate adventurer, who considers himself a skier / mountain biker who teaches Economics in his free time. He and his wife keep a ski chalet in the mountains of Northern Idaho, which now that they live in the Swiss Alps gets far too little use. Read more posts by this author