Stellar distribution in the [Mg/Fe] vs. age (left panel) and the [M/H] vs. age relation (right panel) for the inner (R_g ≤ 7.5 kpc) and the outer (R_g > 7.5 kpc) regions of the Galactic disc. Their respective trends are indicated by the average abundance value per age bin ([2–6], [6–8], [8–10], [10–11], [11–12] and [12–14] Gyr), together with the error bars in [Mg/Fe], [M/H], and age. The overall mean estimated errors are shown in the bottom-left corner.