We calculated the inverse-variance-weighted mean of the genetic-correlation estimates. The genetic correlation across pairs of cohorts will be correlated across all observations that share one of their cohorts in common. Therefore, to obtain correct standard errors, we used the node-jackknife variance estimator described by Cameron and Miller40. As detailed in Supplementary Note, we also estimated the variance of SNP heritability of EduYears across cohorts, and we conducted analyses to assess the extent to which we can predict variation in SNP heritability and genetic correlation of EduYears based on several observable cohort characteristics (Supplementary Tables 24 and 25).
