To put the predictive power of this score in perspective, Fig. 4A shows the mean college completion rate by polygenic-score quintile. The difference between the bottom and top quintiles in Add Health and HRS is, respectively, 45 and 36 percentage points (see Supplementary Figure 11 for analogous analyses of high school completion and grade retention). Fig. 4B compares the incremental R2 of the score to that of standard demographic variables. The score is a better predictor of EduYears than household income and a worse predictor than mother’s or father’s education. Controlling for all the demographic variables jointly, the score’s incremental R2 is 4.6% (Supplementary Figure 12).
