The evolution of the inferred effective-spin distributions as a function of the transition mass scale ﹩\tilde{m}﹩. Error bars indicate the 90% credible intervals. The top panel shows the inferred mean, median, and mode of the effective spin of the population with ﹩{m}_{1}\lt \tilde{m}﹩. The middle panel shows the inferred mean, median, and mode of the population with ﹩{m}_{1}\gt \tilde{m}﹩, illustrating the progressive shift of the high-mass population toward χ_eff ≃ 0 and the increasing uncertainty associated with broader spin distributions at large masses. The bottom panel shows the Pearson first skewness coefficient, quantifying the degree of asymmetry of the inferred χ_eff distributions. While all measurements remain statistically consistent with symmetric distributions, the intermediate-mass regime exhibits tentative evidence for positive skewness associated with the possible excess near χ_eff ∼ 0.5.