N_AGB/N_RGB data of different galaxies compared with the predictions from population synthesis. Top left: comparison between the data and the results obtained by assuming different mass losses during the RGB evolution of low-mass stars, and considering the two cases of an SFH constant (dashed lines) decaying on a timescale of 7.5 Gyr (solid line). Top right: data points compared with the results based on the δm_RGB = 0.25 M_⊙ assumption, for different SFHs versus time relations (for which the CSFH ∝ t^1/3, t, t³ cases were considered). Bottom left: δm_RGB = 0.25 M_⊙ and CSFH ∝ t^1/3, where the two cases that the residual 10% of the stars are formed either within half a gigayear or over the time until 1 Gyr ago are indicated with open points filled with black dots and with open points, respectively. Bottom right: comparison between the data points and the most likely T90 vesus N_AGB/N_RGB relation (see text for details); the uncertainty associated with the latter trend is indicated by the grey shaded area.