  We present a new analysis of the rest-frame B-band COMBO-17 and DEEP2
luminosity functions (LFs) of early-type galaxies (ETGs) as a function of
luminosity and mass. Our aim is to place new stringent constraints on the
evolution of ETGs since z~1. We correct the LF($z$) data for the luminosity
dimming assuming pure luminosity evolution. However, instead of relying on
stellar population synthesis model--dependent assumptions, we adopt the
empirical luminosity dimming rate derived from the evolution of the Fundamental
Plane of field and cluster massive ETGs.Our results show that the amount of
evolution for the ETG population depends critically on the range of luminosity
and masses considered. While the number density of luminous (massive) ETGs with
M_B(z=0)< -20.5 (Mass > 10^11 M_Sun) is nearly constant since z~0.8, less
luminous galaxies display a deficit which grows with redshift and that can be
explained with a gradual population of the ETG "red sequence" by the
progressive quenching of star formation in galaxies less massive than ~10^11
M_Sun. At each redshift there is a critical mass above which virtually all ETGs
appear to be in place, and this fits well in the now popular "downsizing"
scenario. However, ``downsizing'' does not appear to be limited to star
formation, but the concept may have to be extended to the mass assembly itself
as the build-up of the most massive galaxies preceeds that of the less massive
ones. This evolutionary trend is not reproduced by the most recent theoretical
simulations even when they successfully reproduce "downsizing" in star
formation.
