Molecular gas depletion timescales, t_depl = M_gas/SFR, as a function of redshift plotted for our low-L_IR-selected SFGs (squares) and our comparison sample of SFGs and local spirals with CO measurements from the literature (see Sect. 2.2). The molecular gas depletion timescales are computed assuming a “Galactic” CO–H₂ conversion factor for all galaxies, but for z< 0.4 and z> 1 SFGs (pentagons, triangles, and squares) the dotted lines, in addition, show the interval of possible t_depl values as determined with two extreme CO–H₂ conversion factors α = 4.36 (“Galactic” value) and 1.1 (local ULIRG value). A redshift evolution of t_depl is observed in agreement with the expected 1.5 × (1 + z)^-1.5 dependence of Davé et al. (2012), where the normalization is set to the typical depletion time of 1.5 Gyr observed in local galaxies (solid line). Four redshift bins are considered, ⟨ z_0.2 ⟩ = [ 0.055,0.4 ], ⟨ z_1.2 ⟩ = [ 1,1.6 ], ⟨ z_2.2 ⟩ = [ 2,2.5 ], and ⟨ z_3.0 ⟩ = [ 2.7,3.2 ], for the t_depl means shown with the large black crosses with their 1σ dispersion.