Cumulative distribution of molecular gas depletion time (or the inverse of the star formation efficiency), i.e. the ratio of the CO luminosity to the infrared luminosity or the corresponding molecular gas mass with the CO-to-H₂ conversion factor α_CO = 5 M_⊙ (K km s⁻¹ pc²)⁻¹ to the star formation rate (SFR). The distribution of GRB hosts is shown as the dashed red line, whereas that of other galaxies is shown as the solid black line. We treated the upper limits as actual values, so the histogram for GRB hosts is an upper limit. GRB hosts are systematically shifted to the left on this diagram (lower M_H2 given their SFRs), but this is not statistically significant (see Sect. 3.1).