Prices and the European Crisis, Continued

In comments to yesterday’s post on exchange rates and European trade imbalances, paine (the e. e. cummings of the econosphere) says,

pk prolly buys your conclusion. notice his post basically disparaging forex adjustment solutions on grounds of short run impact. but long run adjustment requires forex changes.

I don’t know. I suppose we all agree that exchange rate changes won’t help in the short run (in fact, I’m not sure Krugman does agree), but I’m not convinced exchange rate changes will make much of a difference even in the long run; and anyway, it matters how long the long run is. When the storm is long past the ocean is flat again, and all that.

Anyway, what Krugman actually wrote was

We know that huge current account imbalances opened up when capital rushed to the European periphery after the euro was created, and reversing those imbalances must involve a large real devaluation.

We “know,” it “must”: not much wiggle room there.

So this is the question, and I think it’s an important one. Are trade imbalances in Europe the result of overvalued exchange rates in the periphery, and undervalued exchange rates in the core, which in turn result from the financial flows from north to south after 1999? And are devaluations in Greece and the other crisis countries a necessary and sufficient condition to restore a sustainable balance of trade?

It’s worth remembering that Keynes thought the answer to these kinds of questions was, in general, No. As Skidelsky puts it in the (wonderful) third volume of his Keynes biography, Keynes rejected the idea of floating exchange rates because

he did not believe that the Marshall-Lerner condition would, in general, be satisfied. This states that, for a change in the value of a country’s currency to restore equilibrium in its balance of payments, the sum of the price elasticities for its exports and imports must be more than one. [1] As Keynes explained to Henry Clay: “A small country in particular may have to accept substantially worse terms for its exports in terms of its imports if it tries to force the former by means of exchange depreciation. If, therefore, we take account of the terms of trade effect there is an optimum level of exchange such that any movement either way would cause a deterioration of the country’s merchandise balance.” Keynes was convinced that for Britain exchange depreciation would be disastrous…

Keynes’ “elasticity pessimism” is distinctly unfashionable today. It’s an article of faith in open-economy macroeconomics that depreciations improve the trade balance, despite rather weak evidence. A recent mainstream survey of the empirical literature on trade elasticities concludes,

A typical finding in the empirical literature is that import and export demand elasticities are rather low, and that the Marshall-Lerner (ML) condition does not hold. However, despite the evidence against the ML condition, the consensus is that real devaluations do improve the balance of trade

Theory ahead of measurement in international trade!

(Paul Davidson has a good discussion of this on pages 138-144 of his book on Keynes.)

The alternative view is that the main relationship is between trade flows and growth rates. In models of balance-of-payments-constrained growth, countries’ long-term growth rates depend on the ratio of export income-elasticity of demand and import income-elasticity of demand. More generally, while a strong short-run relationship between exchange rates and trade flows is clearly absent, and a long-run relationship is mostly speculative, the relationship between faster growth and higher imports (and vice versa) is unambiguous and immediate. [2]

So let’s look at some Greek data, keeping in mind that Greece is not necessarily representative of the rest of the European periphery. The picture below shows Greece’s merchandise and overall trade balance as percent of GDP (from the WTO; data on service trade is only available from 1980), the real exchange rate (from the BIS) and real growth rate (from the OECD; three-year moving averages). Is this a story of prices, or income?

The first thing we can say is that it is not true that Greek deficits are a product of the single currency.  Greece has been running substantial trade deficits for as far back as the numbers go. Second, it’s hard to see a relationship between the exchange rate and trade flows. It’s especially striking that the 20 percent real depreciation of the drachma from the late 1960s to the early 1970s — quite a large movement as these things go — had no discernible effect on Greek trade flows at all. The fall in income since the crisis, on the other hand, has produced a very dramatic improvement in the Greek current account, despite the fact that the real exchange rate has appreciated slightly over the period. It’s very hard to look at the right side of the figure and feel any doubt about what drives Greek trade flows, at least in the short run.

Now, it is true that, prior to the crisis, the Euro era was associated with somewhat larger Greek trade deficits than in earlier years. (As I mentioned yesterday, this is entirely due to increased imports from outside the EU.) But was this due to the real appreciation Greece experienced under the Euro, or to the faster growth? It’s hard to judge this just by looking at a figure. (That’s why God gave us econometrics — though to be honest I’m a bit skeptical about the possibility of getting a definite answer here.) But here’s a suggestive point. Greece’s real exchange rate appreciated by 25 percent between 1986 and 1996. This is even more than the appreciation after the Euro. Yet that earlier decade saw no growth of the Greek trade deficit at all. It was only when Greek growth accelerated in the early 2000s that the trade deficit swelled.

I think Yanis Varoufakis is right: It’s hard to see exit and devaluation as solutions for Greece, in either the short term or the long term. There are good reasons why, historically, European countries have almost never let their exchange rates float against each other. And it’s hard to see fixed exchange rates, in themselves, as an important cause of the crisis.

[1] Skidelsky gives the Marshall-Lerner condition in its standard form, but the reality is a bit more complicated. The simple condition applies only in cases where prices are set in the producing country and fully passed through to the destination country, and where trade is initially balanced. Also, it should really be the Marshall-Lerner-Robinson condition. Joan Robinson was robbed!

[2] Krugman wrote a very doctrinaire paper years ago rejecting the idea of balance of payments constraints on growth. I’ve quoted this here before, but it’s worth repeating:

I am simply going to dismiss a priori the argument that income elasticities determine economic growth, rather than the other way around. It just seems fundamentally implausible that over stretches of decades balance of payments problems could be preventing long term growth… Furthermore, we all know that differences in growth rates among countries are primarily determined by differences in the rate of growth of total factor productivity, not by differences in the rate of growth of employment. … Thus we are driven to supply-side explanations…
The Krugmans and DeLongs really have no one to blame but themselves for accepting that all the purest, most dogmatic orthodoxy was true in the long run, and then letting long-run growth take over the graduate macro curriculum.

UPDATE: I should add that as far as the trade balance is concerned, what matters is not just a country’s growth, but its growth relative to its trade partners. This may be why rapid Greek growth in the 1970s was not associated with a worsening trade balance — this was the trente glorieuse, when all the major European countries were experiencing similar income growth. Also, in comments, Random Lurker points to a paper suggesting that another factor in rising Greek imports was the removal of tariffs and other trade restrictions after accession to the EU. I haven’t had time to read the paper properly yet, but I wouldn’t be surprised if that is an important part of the story.

Also, I was discussing this at the bar the other night, and at the end of the conversation my very smart Brazilian friend said, “But devaluation has to work. It just has to.” And she knows this stuff far better than I do, so, maybe.

Do Prices Matter? EU Edition

The Euro crisis. One thing sensible people agree on is that the crisis has little or nothing to do with fiscal deficits  (government borrowing), and everything to do with current account deficits (international borrowing, whether public or private.) And one thing sensible people do not agree on, is how much those current account deficits are due to relative costs, or competitiveness.

A thorough dissection of competitiveness in the European context is here; Merijn Knibbe has some good posts critiquing it at the Real World Economics Review. Krugman, on the other hand, defends the competitiveness story, suggesting that the alternative to believing that relative prices drive trade flows, is believing in the “doctrine of immaculate transfer.” What he means is, the accounting identity that net capital flows equal net trade flows doesn’t in itself provide the mechanism by which trade adjusts to financial flows. A country with an increasing net financial inflow must, in an accounting sense, experience an increasing current account deficit; but you still need a story about why people choose to buy more from, or are able to sell less to, abroad.
So far, one can’t disagree; but the problem is, Krugman assumes the story has to be about relative prices. It’s not the case, though, that relative prices are the only thing that drive trade flows. At the least, incomes do too. If German wages fall, German goods may become more cost-competitive; but in any case, German workers will buy less of everything, including vacations in Greece. Similarly, if Greek wages rise, Greek goods may be priced out of international markets; but in any case Greek workers will buy more of everything, including manufactured goods from Germany. Estimating the respective impacts of relative prices and incomes on trade flows, or the elasticities approach, is one of the lost treasures of the economics of 1978. Both income and price elasticities solve the immaculate transfer problem, since capital flows from northern to southern Europe were associated with faster growth of both income and prices in the south. But their implications for policy going forward are quite different. If the problem is relative prices, a devaluation will fix it; this is what Krugman believes. If the problem is income elasticities, on the other hand, then balanced trade within Europe will require some mix of structural reforms (easier said than done), permanently faster growth in the north than the south, or — blasphemy! — restrictions on trade.
Let’s pose two alternatives, understanding that the truth, presumably, is somewhere in between. In the one case, EU current account imbalances are due entirely to countries’ over- or undervalued currencies. In the other case, current account imbalances are due entirely to differences in growth rates. One thing we do know: In the short run — a year or two — the latter is approximately true. In the short run, the Marshall-Lerner-Robinson condition is almost certainly not satisfied, so a change in prices will have the “wrong” effect on foreign exchange earnings, or at best — if the country’s imports and exports are both priced in foreign currency — have no effect. In the long run, it’s less clear. Do prices or incomes matter more? Hard to say.
So what is the evidence one way or the other? One simple suggestive strand of evidence is the intra- and extra-European trade balances of various countries in the EU. To the extent that trade flows have been driven by price, the deficit countries should have seen larger deficits with other EU countries than with other countries, and the surplus countries similarly should have seen larger surpluses within the union than outside it. Those countries whose currencies would otherwise, presumably, have appreciated relative to other EU members should have shifted their net exports towards Europe; those countries whose currencies would otherwise have depreciated should have shifted their net exports away. Is that what we see?
As is often the case with empirical work, the answer is: Yes and no. From Eurostat, here are trade balances as percent of GDP, within and outside the currency union, for selected countries and selected years.
Intra-EU Trade Balance
1999 2007-2008 2011
Germany  2.0% 4.8% 2.1%
Ireland 19.0% 7.4% 12.6%
Greece -10.0% -9.6% -5.3%
Spain -2.9% -4.0% -0.6%
France -0.3% -3.1% -4.3%
Italy 0.5% 0.5% -0.2%
Netherlands 14.8% 24.5% 27.9%
Austria -3.9% -3.0% -5.0%
Extra-EU Trade Balance
1999 2007-2008 2011
Germany  1.2% 2.8% 4.0%
Ireland 6.1% 7.8% 15.1%
Greece -3.9% -9.1% -4.4%
Spain -2.1% -5.1% -3.8%
France 1.0% -0.1% 0.0%
Italy 0.8% -1.2% -1.4%
Netherlands -11.8% -17.5% -20.5%
Austria 1.4% 2.7% 1.9%
What we see here is sort of consistent with the competitiveness story, and sort of not. Germany did increase its intra-EU net exports about twice as much as its extra-EU net exports over the pre-crisis decade, just as a story centered on relative prices would predict. And on the flipside, the fall in Irish net exports over the pre-crisis decade was entirely with other EU countries, again consistent with the Krugman story. 
But for the other countries, it’s not so simple. The increase of the Euro-era Greek deficit, for instance, was entirely the result of increased imports from non-Euro countries. Euro-area trade, and non-Euro exports, were approximately constant in the ten years from 1999. This is more consistent with a story of rapid Greek income growth, than uncompetitively high Greek prices. Similarly, the movement toward current account deficit of Spain was mostly, and of Italy entirely, a matter of trade with non-EU countries. This is not consistent with the relative-price story, which predicts that intra-EU trade imbalances should have grown relative to extra-EU imbalances. Note also that today, Germany’s net exports to the rest of the EU area are no higher than when the Euro was created, while Greece and Spain have substantially improved their intra-EU balances; but all three countries have moved further toward imbalance with extra-EU countries. This, again, is not consistent with a story in which trade imbalances are driven primarily by the relative price distortions created by the single currency.
Conclusion: Krugman is right that how much relative prices have contributed to intra-European current account imbalances, is a question on which reasonable people can disagree. But as a doctrinaire Keynesian, I remain an elasticity pessimist. It seems to me that we should at least seriously consider a story in which European current account imbalances are due to relatively rapid income growth in the periphery, and slow income growth in Germany, as opposed to changes in competitiveness. A story, in other words, in which a Greek exit from the Euro and devaluation will not do much good.
UPDATE: While I was writing this, Merijn Knibbe had more or less the same thought.

Do Prices Matter?

Do exchange rates drive trade flows? Yes, says Dean Baker David Rosnick. Prices matter:

What happens to the economy as the dollar falls? …Over time, Americans notice that British goods have become more expensive in comparison to domestically produced goods. In other words, the price of U.S.-made sweaters becomes cheaper relative to the price of sweaters imported from Britain. This will lead us to buy fewer sweaters from Britain and more domestically manufactured sweaters.

At the same time, the British notice that American goods have become relatively inexpensive in comparison to goods made at home. This means it takes fewer pounds to buy a sweater made in the United States, so the British will buy more sweaters made in the United States and fewer of their domestically manufactured sweaters.

While American producers notice the increased demand for their exports, allowing them to raise their prices somewhat and still sell more than they had before the dollar fell. Similarly, for British exporters to continue selling they must lower prices.
Thus, as everyone eventually adjusts to the fall in the dollar, the trade deficit shrinks. This is not new economics by any stretch…

Indeed it’s not. Changes in prices induce changes in transaction volumes that smoothly restore equilibrium, is the first article of the economist’s catechism. But how much a given volume responds to a given price change, and whether the response is reliable and strong enough to make the resulting equilibrium relevant to real economies, are empirical questions. You could tell a similar parable about an increase in the minimum wage leading to a lower demand for low-wage labor, but as I’m sure Dean folks at CEPR would agree, that doesn’t it mean it’s what we actually see. You have to look at the evidence.

So what’s the evidence on this point? Dean Rosnick offers a graph showing two big falls in the value of the dollar after peaks in the mid-80s and mid-2000s, and falls in the trade deficit a few years later, in the early 90s and late 2000s. Early 90s and late 2000s … hm, what else was happening in those years? Oh, right, deep recessions. (The early 2000s recession was very mild.) Funny that the same guy who’s constantly chastising economists for ignoring the growth and collapse of a huge housing bubble, when he turns to trade … ignores a huge housing bubble.

Still, isn’t the picture is basically consistent with the story that when the dollar declines, US imports get more expensive and fall, and US exports get cheaper and rise? Not necessarily: Dean’s Rosnick’s graph doesn’t show imports and exports separately. And when we separate them out, we see something funny.

Click the graph to make it legible.

In a world where trade flows were mainly governed by exchange rates, a country’s imports and exports would show a negative correlation. After all, the same exchange-rate change that makes exports more expensive on world markets makes imports cheaper here, and vice versa. But that isn’t what we see at all. Except in the 1980s (when the exchange rate clearly did matter, but not in the way Dean Rosnick supposes; see Robert Blecker) exports and imports very clearly move together. And it’s not just a matter of a long-term rise in both imports and exports. Every period that saw a significant fall in imports — 1980-1984; 2000-2002; 2007-2009 — saw a large fall in exports as well. This is simply not what happens in a world where prices (are the main things that) matter.

(This discrepancy between real-world trade patterns and the textbook vision applies to almost all industrialized countries, and always has. It was noticed long ago by Robert Triffin, who brought it up to argue that movements in relative price levels did not govern trade patterns under the gold standard, as Ricardo and his successors had claimed. But it is just a strong counterargument to today’s conventional wisdom that exchange rates govern trade.)

So if changes in exchange rates don’t drive trade, what does? Lots of things, many of them no doubt hard to measure, or to influence through policy. But one obvious candidate is changes in incomes. One of the big advances of the first generation of Keynesian economists — people like Triffin, and especially Joan Robinson — was to show how, just as prices (the wage and interest rates) fail to equilibrate the domestic economy, leaving aggregate income to adjust, relative prices internationally don’t equilibrate the global economy, leaving output or growth rates to adjust. In the short run, business cycle-type fluctuations reliably involve changes in investment and consumer-durable purchases larger disproportionate to the change in output as a whole; given the mix of traded and non-trade goods for most countries, this creates an allometry in which short-run changes in output are accompanied by even larger short-run changes in imports and exports. For a country that runs a trade deficit in “normal” times, this means that recessions are reliably associated with smaller deficits and booms with larger ones. In the long run, there is also a reliable tendency for increments to income to involve demand for a changing mix of goods, with a greater share of demand falling on “leading sectors,” historically manufactured goods. (The flipside of this is Engels’ law, which states that the share of income spent on food falls as income rises.) Given that both a country’s mix of industries and its trade partners are relatively fixed, this creates a stable relationship between relative growth rates and trade balance movements. Neither of these channels is perfectly reliable, by any means — and the whole point of the industrial policy is to circumvent the second one — but they are still much stronger influences on trade flows than exchange rates (or other relative prices) are.

So with that in mind, let’s look at another version of the graph. This one shows the year-over-year change in the trade balance as a share of GDP, the same change as predicted by an OLS regression on total GDP growth over the past three years, and as predicted by the change in the value of the dollar over the past three years. [1]

It will be legible if you click it.

Not surprisingly, neither prediction gives a terribly close fit. But qualitatively, at least, the predictions based on GDP do a reasonable job: They capture every major worsening and improvement in the trade balance. True, they under-predict the improvement in the trade balance in the later 80s — the Plaza Accords mattered — but it’s clear that if you knew the rate of GDP growth over the next three years, you could make a reasonably reliable prediction about the the behavior of the trade balance. Knowing the change in the value of the dollar, on the other hand,wouldn’t help you much at all. (And just to be clear, this isn’t about the particular choice of three years. Two years and four years look roughly similar, and at a one-year horizon exchange rates aren’t predictive at all.)

Here’s another presentation of the same data, a scatterplot comparing the three-year change in the trade balance to the three-year growth of GDP (blue, left axis) and three-year change in the exchange rate (red, right axis). Again, while the correlation is fairly loose for both, it’s clearly tighter for GDP. All the periods of strongest improvement in the trade balance are associated with weak GDP growth, and vice versa; similarly all the periods of strong GDP growth are associated with worsening of the trade balance, and vice versa. There’s no such consistent association for the trade balance and changes in the exchange rate.

If you want to be able to read the graph, you should click it.

The fit could be improved by using some measure of disposable income — ideally adjusted for wealth effects — in place of GDP, and by using some better measure of relative prices in place of the exchange-rate index — altho there’s some controversy about what that better measure would be. And theoretically, instead of just the three-year change, you should use the individual lags.

Still, the takeaway, if you’re a policymaker, is clear. If you want to improve the trade balance, slower growth is the way to go. And if you want to boost growth, you probably are going to have to ignore the trade balance. Personally, I want door number two. I assume Dean Rosnick doesn’t want door one. But what I’m not at all sure about, is what concrete evidence makes him think that exchange-rate policy opens up a third door.

[1] Technicalities. I separately regressed the changes in imports and exports (as a percent of GDP) over three years earlier, on the percentage change over the same period in GDP and in the Fed’s trade-weighted major-partners dollar index, respectively. It’s all quarterly data, downloaded from FRED. The graphs shows the predicted values from the two regressions. This is admittedly crude, but I would argue that the more sophisticated approaches are in some respects less appropriate for the specific question being addressed here. For example, suppose hypothetically that a currency devaluation really did tend to improve the trade balance, but that it also tended to raise GDP growth, raising imports and offsetting the initial improvement. From an analytic standpoint, it might be appropriate to correct for the induced GDP change to get a better estimate of the pure exchange-rate effect. But from a policy perspective, the offsetting growth-imports effect has to be taken into account in evaluating the effects of a devaluation, just as much as the initial trade-balance improvement. Maybe we should say: Academics are interested in partial derivatives, policymakers in total derivatives?
EDIT: Oops! How did I not notice that this article was by somebody named David Rosnick, not Dean Baker? Makes me feel a bit better — I know Dean does share this article’s basic view of trade and the dollar, but I would hope his take would be a little less dependent on textbook syllogisms, and a little more attentive to actual patterns of trade. Clothing from the UK is hardly representative of US imports; to the extent we do import any, it’s like to be high-end branded stuff that is particularly price-inelastic.

Does the Level of the Dollar Matter?

Mike Konczal has kindly reposted my back-of-the-envelope estimate of how much a dollar devaluation would boost US demand. (Spoiler: Not much.)

I am far from an expert on international trade and exchange rates. (Or on anything else.) Maybe some real economist will see the post and explain why it’s all wrong. But until then, I’m going to continue asking why Krugman and others who claim that exchange rates are an important cause of unemployment in this country, never provide any quantitative analysis to back that opinion up.

More abstractly, one might ask: Is the time it takes for demand to respond to changes in relative prices, minus the time it takes for exchange rate changes to move relative prices, greater than the time it takes for exchange rates changes to move relative costs (or to be reversed)? Just because freshwater economists say No for a bad reason (because relative costs adjust instantly) doesn’t mean the answer isn’t actually No for a good reason.

A Bit More on China

Mike Konczal points me to this interesting piece by Walker Frost in The American Scene, on the Chinese currency peg. I asked earlier how much Chinese appreciation would boost US demand (more on that below). But there’s a prior question, which is whether an end to Chinese currency intervention would lead to appreciation at all. As Frost points out, the dollar purchases by the central bank coexist with restrictions on private investment abroad and strong incentives for FDI by foreign firms. These policies increase net capital inflows and therefore tend to raise the value of the Chinese currency; the Chinese central bank then pushes it back down with its dollar purchases. It’s far from clear which of these effects is stronger, and therefore, whether an across-the-board liberalization would lead the Chinese currency to rise against the dollar, or to fall. In short, we should see Chinese currency interventions not as part of an export-led growth strategy that requires a current-account surplus, but as part of an investment-led growth strategy that would otherwise tend to produce a current-account deficit. [1]

This is a point Anwar Shaikh has also made, when I’ve discussed this stuff with him. Don’t talk about undervaluation, he says, that implies some known free-market equilibrium exchange rate, and there isn’t one; talk about stabilization instead.

Another interesting discussion of the Chinese currency peg is in this Deutsche Bank report, which tends to confirm my skepticism about the effect of currency adjustment on US-China trade flows. They note that “RMB appreciation tends to … reduce nominal wages in the export sector,” confirming my sense that exchange rate changes don’t reliably move relative costs. And they use an estimate of -0.6 for exchange rate elasticity of Chinese exports. I don’t want to put too much weight on this number — I’m not sure how it’s derived — and they don’t give any estiamtes for US-China flows specifically; but given the well-established empirical fact that exchange-rate elasticity is unsually low for US imports, we have to conclude that the number for Chinese exports to the US is substantially lower. So if you believe the Deutsche Bank number for Chinese exports as a whole, my estimate of -0.17 for Chinese exports to the US is probably in the right ballpark. Which, again, means that even a very large Chinese appreciation would have only a trivial impact on US aggregate demand.

[1] The same goes for tariffs and other trade restrictions imposed by Latin American countries as part of import-substitution industrialization.

… and How About a Higher Yuan?

Another day, another Paul Krugman post blaming China for US unemployment. And maybe he’s right. But it would be nice to see some numbers.

On the same lines as my earlier post about the effect of dollar devaluation on aggregate demand, we can make a rough estimate of trade elasticities to calculate the effect of a Chinese revaluation.

Unfortunately, there aren’t many recent estimates of bilateral trade elasticities between the US and China. But common sense can get us quite a ways here. In recent years, US imports from China have run around 2 percent of GDP, and US exports to China a bit under 0.5 percent. So even if we assume that (1) a change in the nominal exchange rate is reflected one for one in the real exchange rate, i.e. that it doesn’t affect Chinese prices or wages at all; (2) a change in the real exchange rate is passed one for one into prices of Chinese imports in the US; (3) Chinese goods compete only with American-made goods, and not with those of other exporters; and (4) the price elasticity of US imports from China is a very high 4.0; then a 20 percent appreciation of the Chinese currency still boosts US demand by less than 1 percent of GDP.

And of course, those are all wildly optimistic assumptions. My own simple error-correction model, using 1993-2010 data on US imports from China and the relative CPI-deflated bilateral exchange rate, gives an import elasticity of just 0.17. [1] If the real figure is in that range, then a Chinese appreciation of 20 percent will reduce our imports from China by just 0.03 percent of GDP — and of course much of even that tiny demand shift will be to goods from other low-wage exporters.

I don’t claim my estimate is correct. But is it too much to ask that Krugman tell us what estimates he is using, that have convinced him that the best way to help US workers is to foment a trade war with China?

[1] This is a real exchange-rate elasticity, not a price elasticity, so it accounts for incomplete passthrough and offsetting movements in Chinese real wages. It assumes, however, that changes in the nominal exchange rate don’t affect inflation in either country; to that extent, it’s more likely an overestimate than an underestimate

How Much Would a Lower Dollar Boost Demand?

Lots of economists of the liberal Keynesian persuasion (Paul Krugman, Dean Baker, Robert Blecker [1] — very smart guys all) think dollar devaluation is an important step in getting back toward full employment in the US. But have any of them backed this up with a quantitative analysis of how much a lower dollar would raise demand for American goods?

It’s not an easy question, of course, but a first cut is not that complicated. There are four variables, two each for imports and exports: How much a given change in the dollar moves prices in the destination country (the passthrough rate), and how much demand for traded goods responds to a change in price (the price elasticity.) [2] We can’t observe these relationships directly, of course, so we have to estimate them based on historical data on trade flows and exchange rates. Once we choose values of them, it’s straightforward to calculate the effect of a given exchange rate change. And the short answer to this post’s title is, Not much.

For passthrough, estimates are quite consistent that dollar changes are passed through more or less one for one to US export prices, but considerably less to US import prices. (In other words, US exporters set prices based solely on domestic costs, but exporters to the US “price to market”.) The OECD macro model uses a value of 0.33 for import passthrough at a two-year horizon; a simple OLS regression of changes in import prices on the trade-weighted exchange rate yields basically the same value. Estimates of import price elasticity are almost always less than unity. Here are a few: Kwack et al., 0.93; Crane, Crowley and Quayyum, 0.47 to 0.63; Mann and Pl├╝ck, 0.28; Marquez, 0.63 to 0.92. [3] (Studies that use the real exchange rate rather than import prices almost all find import elasticities smaller than 0.25, which also supports a passthrough rate of about one-third.) So a reasonable assumption for import price elasticity would be about 0.75; there is no support for a larger value than 1.0. Estimated export elasticities vary more widely, but most fall between 0.5 and 1.0.

So let’s use values near the midpoint of the published estimates. Let’s say import passthrough of 0.33, import price elasticity of 0.75, and export passthrough and price elasticity both of 1.0. And let’s assume initial trade flows at their average levels of the 2000s — imports of 15 percent of GDP and exports at 10.5 percent of GDP. Given those assumptions, what happens if the dollar falls by 20 percent? The answer is, US net exports increase by 1.9 percent of GDP.

1.9 percent of GDP might sound like a lot (it’s about $300 billion). But keep in mind, these are long-run elasticities — in general, it takes as much as two years for price movements to have their full effect on trade. And the fall in the dollar also can’t happen overnight, at least not without severe disruptions to financial markets. So we are talking about an annual boost to demand of somewhere between 0.5 and 1.0 percent of GDP, for two to three years. And then, of course, the stimulus ends, unless the depreciation continues indefinitely. This is less than half the size of the stimulus passed last January (altho to be fair, increased demand for tradables will certainly have a higher multiplier than the tax cuts that made up a large share of the Obama stimulus.) The employment effect woul probably be of the same magnitude — a reduction of the unemployment rate by between 0.5 and 1.0 points.

I would argue this is still an overestimate, since it ignores income effects, which are much stronger determinants of trade than exchange rates are — to the extent the US grows faster and its trading partners grow more slowly as a stronger US current account, that will tend to cancel out the initial improvement. I would also argue that the gain to US employment from this sort of rebalancing would be more than offset by the loss to our trade partners, who are much more likely to face balance of payments constraints on domestic demand.

But those are second-order issues. The real question is, why aren’t the economist calling for a lower dollar providing quantitative estimates of its effects, and explicitly stating their assumptions? Because on its face, the data suggests that an overvalued dollar plays only a modest role in US unemployment.

[1] I was going to include Peter Dorman on this list but I see that while he shares the IMO misplaced concern with global imbalances, he says, “Will a coordinated dollar devaluation do the trick? Maybe, if you can get coordination (no easy feat), but it is also possible that US capacity in tradables has deteriorated too far for price adjustment alone to succeed.” Which is a more realistic view of the matter than the one Krugman seems to hold. On the other hand, Dorman was also writing just a couple years ago about The Coming Dollar Crash. That dog that didn’t bark is something I’ll hopefully be writing about in a future post.

[2] Many studies collapse passthrough and price elasticity into a single measure of real exchange rate elasticity. While this is a standard approach — about half the published papers take it — I would argue it’s not the right one for either analytic or policy purposes. Analytically, the real exchange rate elasticity doesn’t distinguish between the behavior of buyers and sellers: A low value could mean either that consumers are not responsive to price, or that sellers are holding price stable in the face of exchange rate changes. And on the other side, it’s the nominal, not real, exchange rate that’s accessible to policy. Policy-induced movements in the nominal exchange rate only translate into movements in the real rate if we assume that price levels (and real wages, if we’re deflating by labor costs) don’t respond to movements in the exchange rate, which is not generally a safe assumption.

[3] Price elasticities are all negative of course. I’m omitting the negative sign for simplicity.