Estimated mass inflow rates, Ṁ_model, which may have occurred during the successive build-up of the stellar population of the ONC. Inflow began about 3 Myr ago when the molecular-cloud filament, at present in the shape of an integral, establisheditself. This formed the first (blue) population. The presently on-going inflow, shown in red, has been forming the third (present-day) population and is larger than the directly measured value by Hacar et al. (2017a). This may be a sign of on-going photo-ionisation of the inflow through the star θ¹ C Ori. The upper and lower bounds on Ṁ_{g, flow} are the one-sigma and the 5–95% bounds, respectively, on the time-scales over which the populations formed (Table 1 in Beccari et al. 2017).