Star formation efficiencies, (left y-axis), or molecular gas depletion timescales, t_depl = M_gas/SFR, assuming a “Galactic” CO–H₂ conversion factor for all galaxies (right y-axis), as a function of IR luminosities of our low-L_IR-selected SFGs (squares) compared to our compilation of galaxies with CO measurements from the literature (see Sect. 2.2). This illustrates in another way the large dispersion about the L_IR– relation observed in Fig. 6.