Column density ratios of [CH₂DOH]/[CH₃OH] (upper panel) and [CHD₂OH]/[CH₂DOH] (lower panel) as a function of source types. Filled symbols indicate single-dish observations and open symbols indicate interferometric observations. Symbols with downward arrows show the derived upper limits. References: Bianchi et al. (2017a) for SVS13-A; Taquet et al. (2019) and Parise et al. (2006) for IRAS4A and IRAS2 (also IRAS4B, all located in NGC 1333); Bianchi et al. (2017b) for HH212; Manigand et al. (2019), Jørgensen et al. (2016), Drozdovskaya et al. (2022) for IRAS 16293A and IRAS 16293B; Drozdovskaya & Schroeder (2021) for comet 67P/C-G. For an exhaustive plot of [CH₂DOH]/[CH₃OH] for all available measurements we refer to Drozdovskaya & Schroeder (2021) and their supplementary data.