Andrew Rose has long argued that a common currency has a large effect on increasing trade. Recently, Rose has called into question the reliability of this conclusion, as new techniques have emerged for estimating gravity equations. This article uses the sector‐specific gravity model developed by Anderson and Yotov (2010a) to investigate if disaggregated trade can provide a reliable estimate of a common currency's effect. Disaggregating trade alone is insufficient to obtain a reliable estimate of a currency union, regardless of econometric technique, when the effect of a common currency on trade is uniform across all unions. Disaggregating the universe of currency unions with individual effects provides a reliable ranking of currency unions, independent of estimation method, by the effect that each union's currency has on increasing trade. These rankings differ across sectors.