The monthly file that was used for constructing the results of the paper about EM20 ( the 20 emerging market currencies ) involves an error. The monthly file for EM20 was cre ated by combining two daily data files, one from AIG Financial Products and the other from WM/Reuters. As stated in Section IIB of the paper, if there is a currency-date pair for which the exchange rate data are not available from the former source but are available from the latter source (the WM/Reuters daily file ), our intention was to import the exchange rate data from the WM/Reuters file. However, we inadvertently imported the WM /Reuters data even for currencydates for which the exchange rate data are available from the former source. Also, in the process of importation, very few repeated exchange rate observations from WM /Reuters were inadver tently included in the monthly file. This error has been corrected. The correction is now reflected in the monthly data and the data appendixes, along with the set of Matlab codes used for mapping from the two daily files to the monthly file, that are downloadable from the American Economic Journal: Macroeconomics