Fig. 3. Predictive performance for African-ancestry individuals against sample size for 15 traits in UK Biobank.

a We fixed the number of European-ancestry (EUR) individuals in the training set at ~50,000 (26,388 for female genital prolapse (FGP)) and varied the number of African-ancestry (AFR) individuals from 0 to ~4700 (2900). The predictive performance, evaluated in terms of partial r², on African-ancestry individuals increased markedly for mean corpuscular volume (MCV) and platelet crit; and stayed largely stable (or increased slightly) for the remainder. b Here, we instead fixed the number of African-ancestry individuals in the training set at ~4700 (2900 for FGP) for each trait and varied the number of European-ancestry individuals so that the proportion of European-ancestry individuals in the training set ranged from 0% to 90%. The effect on performance on African-ancestry individuals again varied by trait, showing a clear improvement for MPV and height, and a moderate decrease for MCV. Error bars correspond to the range across five cross-validation rounds of training set construction and PGS estimation. Phenotype acronyms: mean platelet volume (MPV), mean corpuscular volume (MCV), body mass index (BMI), atrial fibrillation (AFib), diverticular disease of the intestine (DDI), female genital prolapse (FGP).