Redshift evolution of the cosmic molecular gas mass density of galaxies. The blue horizontal line represents predictions from our cone of mock galaxies, while observational constraints are presented by rectangles. The gray rectangles are for the dust-based estimates of Magnelli et al. (2020), the light gray rectangles are for the COLDz CO survey (Riechers et al. 2019), the light blue rectangle for the CO-based estimates of Boogaard et al. (2023), the red-shaded rectangles are for the ASPECS CO pilot survey (Decarli et al. 2020), while the pink rectangles are for the ASPECS CO LP survey (Decarli et al. 2020). The width of the rectangles indicates the redshift bin size and the height the 1-σ confidence region.