Left: relation between the SFE = SFR/M_gas and the stellar mass (M_∗) for main-sequence galaxies at z = 1. Colored diamonds show the measured SFEs and M_∗ of our stacked sample, the color being associated with the stellar mass as in Fig. 6. The best-fit power law to our measurements, excluding the most massive point, is given with a black solid line (Eq. (9)). Right: gas fraction (f_gas ≡ M_gas/ (M_gas + M_∗)) as a function of the stellar mass (M_∗) for main-sequence galaxies at z = 1. The legend is the same as in the left figure, and here the solid black line gives the value of f_gas computed using the best-fit M_gas − M_∗ relation, also excluding the most massive point in the fit. The resulting expression of f_gas is given in Eq. (10). We also show the measured gas fractions by Magdis et al. (2012) at z = 2 with a dashed gray line and by Santini et al. (2014) at z = 1 with a dot-dashed gray line.