Because educational institutions vary across places and time, the effects of specific SNPs may vary across environments. Consistent with such heterogeneity, for the lead SNPs, we reject the joint null hypothesis of homogeneous cohort-level effects (P value = 9.7×10−12; Supplementary Figure 4). Moreover, we found that the inverse-variance-weighted mean genetic correlation of EduYears across pairs of cohorts in our sample is 0.72 (SE = 0.14), which is statistically distinguishable from one (P value = 0.03).
