than the second most polygenic of the 16 independent traits (chronotype, having M50%=553K), consistent with ref. 34. We performed 7 secondary analyses, described in the Supplementary Note and in Supplementary Tables 32–33. We note that far fewer than 2 million SNPs may causally explain 50% of the common SNP heritability of number of children, because M50% is a (possibly loose) upper bound.
