A meta-analysis of the effect of common currencies on international trade

"Thirty-four recent studies have investigated the effect of currency union on trade, resulting in 754 point estimates of the effect. This paper is a quantitative attempt to summarize the current state of debate; meta-analysis is used to combine the disparate estimates. The chief findings are that: (a) the hypothesis that there is no effect of currency union on trade can be rejected at standard significance levels; (b) the combined estimate implies that a bilateral currency union increase trade by between 30% and 90%; and (c) the estimates are heterogeneous and not consistently tied to most features of the studies"--National Bureau of Economic Research web site.