H I-to-stellar mass ratio (M_HI/M_*; top panels), sSFR (SFR/M_*; second row of panels), and H I gas depletion time (M_HI/SFR; bottom panels) plotted as a function of stellar mass, for the low-z calibrating sample (left) and the DEEP2 galaxies at the two higher redshifts (centre and right-hand panels). The small black dots are for the low-z calibrating sample or the blue galaxies at high redshifts, and the red line in each panel shows the best fitting with a linear relation. The stars and the two solid lines plotted in green show the median and 1σ scatter for a number of stellar mass bins, respectively. For comparison, the mean measurements of star-forming galaxies at redshift z ∼ 1 by Chowdhury et al. (2020) are plotted as filled red circles.