[O i] luminosity vs. L_bol (top-left), T_bol (top-middle), M_env (top-right) and integrated intensity in the H₂O 1₁₀ −1₀₁ transition (bottom-left). Bottom-middle: [O i] luminosity normalised by L_bol vs. the evolutionary indicator proposed by Bontemps et al. (1996). The plots include data from the WILL, WISH and DIGIT samples, as well as from the literature from Podio et al. (2012) and the HOPS (Watson et al. 2016) and FOOSH (Green et al. 2013b) surveys where available. The number of sources and correlation statistics in the upper-right of each panel include only Class 0/I sources so as to be conservative. The horizontal grey line in the top panels indicates the upper limit for disk emission from Howard et al. (2013). Bottom-right: histogram of L[O i] as a function of spectral type, including sources from all surveys.