The fraction of stars younger than 5 Gyr and 8 Gyr, respectively, at different metallicities. The thick blue and red lines represent the mean values from 10 000 age-metallicity distributions where individual ages and metallicities have been re-sampled using the [Fe/H] uncertainties and the individual age probability distributions (see text for more details). The shaded areas show the formal errors of the mean (1-sigma dispersion divided by ).