Evolution of the modified KS relation. The colour code is the same as in Fig. 2. In the graph at 3 Myr, we report the values of ϵ_ff of the 12 Galactic clouds studied in Pokhrel et al. (2021), excluding contours with Σ_avg above their reliability criterion (grey lines). The grey shaded areas represent the uncertainties they gave for the ϵ_ff measures. The axis ratios are kept the same as in Fig. to facilitate a visual comparison of slopes with the respective counterparts in the KS relation.