Cosmic density of molecular gas (ρ_mol) from REBELS at z = 6.5–7.5 compared to measurements from the literature. The filled red box region represents the [C II]-based measurement of this work. Literature data points come from various CO, dust, and [C II] surveys, including ASPECS CO (Decarli et al. 2020) and dust measurements (Magnelli et al. 2020), COLDz (Riechers et al. 2019), PHIBSS (Lenkić et al. 2020), ALMACAL (Klitsch et al. 2019), A3COSMOS (Liu et al. 2019), and dust measurements from Scoville et al. (2017) and ALPINE (Yan et al. 2020). The dotted green curve shows the cosmic SFR density (Madau & Dickinson 2014), scaled by a typical molecular gas-depletion timescale of 0.5 Gyr (Tacconi et al. 2020). REBELS measurements, which extend to z ~ 7, indicate a sustained decline of ρ_mol at earlier epochs.