Depletion time as a function of TIR and FIR luminosities. Solid lines are fits to the (U)LIRG sample, where log(t_dep)  =  (−0.25 ± 0.10)log(L_TIR)+(11.54 ± 1.05) and log(t_dep)  =  (−0.26 ± 0.09)log(L_FIR)+(11.61 ± 0.96). Dashed lines are a fit to the combined sample and yield log(t_dep)  =  (−0.19 ± 0.07)log(L_TIR)+(10.89 ± 0.77) and log(t_dep)  =  (−0.20 ± 0.06)log(L_FIR)+(10.95 ± 0.67). This trend implies that gas is consumed faster in (U)LIRGs and thus star formation is more efficient in these systems, compared to lower luminosity spiral galaxies.