The Saga of Currency Unions and Trade

Douglas Campbell:

The Saga of Currency Unions and Trade: One of the first full papers I wrote was on currency unions and trade. I was taking Alan Taylor's field course at UC Davis, which was essentially and Open-Economy Macro History course, and the famous Glick/Rose findings that currency unions double trade was on the syllabus. Not to be outdone, Robert Barro and coauthors then found that currency unions increase trade on a 7-fold and 14-fold basis! This raised the prospect that Frenchman may suddenly go out and buy a dozen or more Volkswagens instead of settling for just one after the adoption of the Euro. Another paper, published in the QJE, found that currency unions even raise growth, via trade. In that case, one can only imagine what the Greek economy would look like if they hadn't joined the Euro. No result, it seems, can be too fanciful.

Always a doubting Thomas, I was instantly skeptical. ...

So, I fired up Stata, and after a solid 30 minutess, I discovered part of what was driving the seemingly magical effect. Roughly one-quarter of the CU changes were of countries that had former colonial relationships... It turns out that the impact of the "former colony" dummy in the gravity equation has been decaying slowly over time. This led to a more interesting insight -- that history matters for trade... For other country pairs aside from colonies, there were other problems. ...

In any case, in 2015, I deleted this paper and my regression and code from my webpage, and assigned the paper to my brilliant undergraduate students. They alerted me to the fact that Glick and Rose had recently written a mea culpa, where the authors declared that they could no longer have confidence in the results. ... However, Glick and Rose changed their minds, and decided instead to double-down on a positive, measurable impact of currency unions on trade. This time, they concluded that the Euro has increased trade by a smaller, but still magical, 50%. ... 

In any case, Jeff Frankel at Harvard apparently used to assign his Ph.D.'s students a "search-and-destroy" mission on the original CU effect. Thus, thanks to the fact that Andrew Rose still provides his data online -- for which I'm grateful -- I've just assigned my students a similar mission on the new EMU result. Thus, we get to see if they can overturn anything that the good referees at the European Economic Review may have overlooked. If I were a gambling man, and I am, I would put my money on my sharp undergraduates at the New Economic School over the academic publication process. If I were Croatia, or Greece, contemplating the relative merits of joining/staying in the Euro, I would write off the academic literature on this topic completely.