Metallicity distributions predicted by the best-fit models (coloured histograms) computed at 4 kpc (upper panel), 8 kpc (middle panel), and 12 kpc (lower panel). The observed APOGEE DR16 distributions are shown by the black empty histograms. The vertical lines indicate the median values of each distribution. In each plot, the distributions are normalised to the corresponding maximum number of stars, N_max.