Mass fractions m_j as a function of look-back time for the four mass bins, with mass increasing from top to bottom (in the case of BC03 models). Colored vertical lines (colour-coded as in Fig. 10) are the m_j obtained from the full-spectrum fitting for each mass bin, put in phase according to their P50. In each mass bin, black vertical lines mark the P50 of the distribution, obtained from data as an average of the P50 of all the redshift bins, while black horizontal lines are the median dispersions [P50 – P16] and [P84 – P50]. The corresponding asymmetric Gaussians (grey) are overplotted on the m_j distributions. On the top of the figure, the z_F corresponding to each age_f is indicated.