Ratios of ETG number densities at a given redshift with respect to a z ~ 0 SDSS sample. The horizontal solid lines show the unit ratio. The shaded areas show the cosmic variance as calculated in Appendix A2. The squares show the results from MUSYC for the r-band (solid symbols) and the B-band (open symbols, slightly displaced on the x-axis) from PML estimates of the LF; the errorbars for the results in the two bands (r and B) are similar, but are shown only for the r-band to improve clarity. The crosses show the results from the r-band LF calculated using the photo-z based maximum likelihood method. The circles correspond to results from the COMBO-17 ETG LF estimate, triangles to DEEP2, and stars to the SXDS. Top panel: samples of bright ETG galaxies. Lower panels: faint ETGs. Comparing the shaded area and symbols, a marginal agreement between the evolution in models and observations can be noticed.