⟨f_gas⟩ evolution when fitting all data points, as in Fig. 2 (thick black curve), only local objects (dashed red curve), only intermediate-to-high redshift galaxies (green dash-dot-dotted curve), or ignoring either pSB galaxies (dotted yellow curve) or dust-derived constraints (G18 and M20; dash-dotted blue curve). For comparison, the best-fit model with SF gas depletion is shown as a thick dashed light-blue line. The tracks shown here are for a 1.5 × 10¹¹ M_⊙ QG, while the gray points show the various samples used, as in Fig. 2.