Comparison of three different M_gas estimates: the first is based on CO (rescaled to a common α_CO,MW = 4.36, including a metallicity correction; Genzel et al. 2012, 2013, 2015); the second based on the scaling of depletion times, τ_dep; and the third derived from M_dust, using the δ_GDR-Z and M^∗-Z relations in the PP04 metallicity scale. Left: datasets include GOODS-N (blue filled circles) and GOODS-S (red filled squares) 160 μm-detected sources; Herschel-detected SMGs (green filled pentagons; Magnelli et al. 2012a); CO-detected galaxies (different blue symbols, see below); and the Magnelli et al. (2014) stacked points (gray crosses). The right-hand panels only include CO-detected sources, namely: PHIBSS galaxies (blue triangles, Tacconi et al. 2013); BzK galaxies (blue squares, Daddi et al. 2010); other star-forming galaxies (blue filled circles, Magnelli et al. 2012b); lensed galaxies (empty blue circles, Saintonge et al. 2013); and SMGs (green upside down triangles, Bothwell et al. 2013). The dashed and dotted lines in the lower-right panel mark the ± 0.3 and ± 0.6 dex deviations from the 1:1 locus (solid line).