Parent distributions of Γ. Upper panel: parent distributions for a subsample that is the same size as the XMM-COSMOS data sample and is randomly selected from the simulation. The true distribution is plotted as the filled histogram in orange, and the reconstructed Γ distribution obtained by applying FFPI is shown as the black line. We also show the reconstructed distribution of Γ using the Bayesian parametric fitting in blue. Error bars and the shaded blue area show the 68.3% credible intervals. All distributions are normalized to unit area. Lower panel: corner plot of the parameters of the second to the fifth bins (p₂ − p₅, converted to probability density for consistency with the lower panel), which include the vast majority of the sources.