With the 10th anniversary of the launching of the euro, everyone is taking stock. The record of the euro shows both pluses and minuses. Looking back, the euro has in many ways been more successful than predicted by the sceptics—many of them American economists. The historic transition to a monetary union among 11 countries in 1999 went smoothly, the euro instantly became the world’s number two international currency and the officials of the European Central Bank (ECB) have from the beginning worked as citizens of Europe rather than as representatives of home constituencies. After a rocky start, the ECB has achieved a strong reputation, the euro has achieved a strong value and new members to the east have achieved membership in the club.

Illustration: Jayachandran / Mint

One of the most interesting questions at the inception of the euro was whether the elimination of currency risk and of foreign exchange transaction costs would promote trade among members. Facilitating trade had been one of the most important of the original motivations of founders such as Jacques Delors. Prior to 1999, however, most economists believed that the effects of currency barriers between countries, if even greater than zero, were small—small, for example, relative to trade barriers.

In 2000, Andrew Rose published what turned out to be one of the most influential empirical papers of the decade: One Money, One Market… Applying the gravity model to a data set that was sufficiently large to encompass a number of currency unions led to an eye-opening finding: Members of currency unions traded with each an estimated three times as much as with otherwise-similar trading partners. Many found the tripling estimate implausibly large. No sooner had Rose written his paper than the brigade to “shrink the Rose effect"—or to make it disappear altogether—descended en masse. This research was of course motivated by the coming of the euro in 1999, even though estimates were necessarily based on historical data from (much smaller) countries that had adopted (or left) currency unions in the past.

By roughly the five-year mark, enough data had accumulated to allow an analysis of the early effects of the euro on European trade patterns. The general finding was that that bilateral trade among euro members had indeed increased significantly, but that the effect was far less than the one that had earlier been estimated by Rose and others on the larger data set of smaller countries. None came anywhere near the tripling estimates of Rose.

There are three leading explanations for the discrepancy between the estimates of the euro’s effects and those from historical estimates.

1) It takes time for the effects on trade to rise to their full magnitudes; 2) monetary unions have much smaller effects on large countries; and 3) the Rose estimates on smaller countries were spuriously high as a result of the endogeneity of the decision to form a currency union. In other words, bilateral currency links have historically been the result of bilateral trade links rather than the cause. I have tried to assess the importance of these factors in explaining the discrepancy.

Surprisingly, the evidence does not support an important role for any of the explanations. The effect of the euro on trade between members remains highly significant statistically, but no higher in magnitude than it was four years ago; it is steady at 10-15%. It is entirely possible that the future will reveal substantially larger effects as substantially more time goes by. But at the moment, there is little evidence to support the lags explanation.

Pursuant to the question of country size, I tested for an effect of the interaction of size and currency union membership. There is no tendency, overall, for currency unions to have larger effects on the trade of small countries than large.

The question of endogeneity is trickier. I tried a “natural experiment", designed to be as immune as possible from the argument that the choice of currency is endogenous with respect to trade. The experiment is the effect on African CFA members’ bilateral trade of the French franc’s 1999 conversion to the euro. The long-time link of CFA currencies to the French franc has clearly always had a political motivation. So, CFA trade with France could not in the past reliably be attributed to the currency link. But in January 1999, 14 CFA countries woke up in the morning and suddenly found themselves with the same currency link to Germany, Austria, Finland, Portugal and others as they had with France. There was no economic/political motivation on the part of the African countries that led them to an arrangement whereby they were tied to these other European currencies. Thus, if CFA trade with these other European countries has risen, that suggests a euro effect that we can declare causal.

Thus, none of the three explanations appears to explain the gap between the recent euro estimates and the historical estimates. Perhaps time will offer more evidence for one or more of the explanations in the future.

Edited excerpts. Published with permission from VoxEU.org. Jeffrey Frankel is a professor of economics at the Kennedy School of Government, Harvard University. Comment at theirview@livemint.com