Properties of a mixture of two populations of Class II objects with different ages. Left: Median disk masses of distributions sampling N = 10⁵ disks with replacement from ℓ > 213.1° and Upper Sco (Barenfeld et al. 2016) with ratio f (black), and the median disk masses and uncertainties for Upper Sco (red), SODA between ℓ < 210° (blue), and between ℓ > 213.1° (green). Right: Kaplan-Meier estimators for the disk mass distributions resulting from a draw of 500 samples with f = 0.77 (dark gray), in SODA between ℓ > 213.1° (green), ℓ < 210° (blue), and in Upper Sco (red).