Left: H I mass divided by stellar mass as a function of redshift for CHILES, xCOLD GASS, COOL BUDHIES, and HIGHz. The dark brown lines are the typical gas ratio for a gas-rich galaxy (log(M_*/M_⊙) = 10.3 from a stellar mass-selected sample of Catinella et al. (2018). The light brown lines are the gas ratio for a gas-rich galaxy of the same mass based on Maddox et al. (2015). Right: H₂ mass divided by stellar mass for the same samples. Here the dark brown line is the molecular gas-to-stellar ratio for a log(M_*/M_⊙) = 10.3 main sequence galaxy, and the light brown line is for a starburst galaxy, both based on the empirical evolutionary models of Scoville et al. (2023). The dotted brown lines are for no H I evolution; the dot-dashed brown lines are for a “fast” factor of two evolution between z = 0 to z = 1. See the text for details. The black short-dashed lines indicate the functional fits to the evolution of the cosmic density from Walter et al. (2020). In the left plot, the black long-dashed lines are the fit to the same H I data by Péroux & Howk (2020). The rest of the symbols are the same for both plots: purple ‘x’s and blue dots are detections in the xCOLD GASS sample below and above log(M_*/M_⊙) = 10, respectively. Green symbols are CHILES z = 0.12 galaxies (this work); orange symbols are COOL BUDHIES galaxies. In both CHILES and COOL BUDHIES the open circles are galaxies with both CO and H I detections, the downward arrows and ‘x’/downward triangles are galaxies with CO upper limits. In CHILES, the green ‘x’s/downward arrows have the same mass range as the xCOLD GASS ‘x’s. The green square is the stacked CO non-detections. Gray squares are HIGHz galaxies. Red symbols are the CHILES z = 0.376 detection corresponding to conversion factors for interacting galaxies (α_CO = 0.8, bottom) and the Galactic value (α_CO = 4.3, top) (Fernández et al. 2016). The uncertainties for the CHILES galaxies in the left panel are ±0.15 − 0.25 dex, and ±0.1 − 0.15 dex in the left panel. See text for further details.