Average light (upper panel) and mass (bottom) fractions (defined with respect to λ = 5635 Å, the normalizing wavelength) due to stars in different age ranges as a function of Hubble type. Age ranges are coded by color: the youngest ones, <32 Myr, are in violet (hardly visible in the bottom panel because they carry little mass). Populations from 32 to 900 Myr are shown in green; those from 0.9 to 2 Gyr in orange, and older ones in red.