We considered the 1,171 studies indexed in the catalog of Published Genome-Wide Association Studies as to February 2012 (http://www.genome.gov/26525384, last accessed 14th February 2012) and classified them according to the trait under study. Each study was classified according to the genetic ancestry of the samples, considering only individuals used in the GWAS stage. Studies performed on a mixed panel were considered only if separate ancestry-specific analyses were provided and we recorded them as independent studies. We observed a strong bias towards GWAS performed with “European” (78.4%) and “East Asian” (14.9%) individuals, while much fewer studies are available for “African” (4.3%), “Hispanic” (1.2%), “Middle Eastern” (0.5%), “Native American” (0.4%) and “Oceanian” (0.3%) ancestries. Therefore, and to increase the reliability of our results, we focused on GWAS performed with peoples of European and East Asian ancestry to select frequently studied diseases. We ascertained only dichotomous disease traits, avoiding anthropometric traits such as height. To produce reliable replicability estimates across ancestries we included in our analysis the 28 diseases for which two or more GWAS were available in any of the two ancestral
