Effect of stellar radial migration on the SFH across the MW disc. Left and Middle: fractional difference between the true SFR and the present-day age distributions of mono-radius populations, shown as a function of lookback time. Positive values indicate an overestimate of SFR: more stars are currently observed at a given radius than were actually formed there at that epoch, due to inward or outward migration. The horizontal dashed lines in the left panel mark the boundaries of radial regions shown in the middle panel. Right: mean age present-day (blue line) and by-formation (red line) profiles together with the 16–84th percentiles highlighted with the filled areas of the same colours. The mean metallicity profiles are given in Fig. A.3.