The scaling relation between M_HI (top) and M_H2 (bottom) as a function of stellar mass for observations. Red triangles show measurements, and crosses show upper limits. The solid red line shows the adopted level of completeness limits of the observations for HI (Eq. (1)) and H₂ (Eq. (2)) masses, respectively. Shaded areas show the scaling relations for C22 (light blue, Eq. (3) in the top panel, Eq. (4) in the bottom panel) and for GAEA (light grey, Eq. (5) in the top panel, Eq. (6) in the bottom panel).