Temporal evolution in the simulation of Fig. 5 of the full width of the main shell (jet-ambient interface, crosses) and outer shell (forward shock, circles) measured at altitudes z = 800 au (black) and z = 20 000 au (red). Analytical predictions for the equivalent “modified X-wind” model of Lee et al. (2001) are shown as dotted black and red lines of slope t^l/2 (see text). The full range of CO outflow widths observed at z = 800 au by Dutta et al. (2020) is indicated by the light grey band (with second and third quartiles in darker grey, and median as a thin green line). The full width of the HH46-47 outflow at z = 20 000 au, from Zhang et al. (2016), is shown in blue.