In order to estimate the gcp, we utilize the following relationship between the mixed fourth moments of the marginal effect size distribution and the parameters q1 and q2: (2)E(α13α2)=κπq13q2+3ρg, where π is the effect of a SNP on L and κπ = E(π4) − 3 is the excess kurtosis of π (see Methods). This equation implies that if ∣E(α13α2)∣≥∣E(α1α23)∣, then q12≥q22 and gcp ≥ 0.
