Location of the HE sample in the plane M_B vs. redshift (red spots), superimposed to a random subsample of the Véron-Cetty & Véron (2010) catalog (gray dots). Data points representing our low-z RQ control sample and GTC sample of faint quasars at z ~ 2.3 are also shown as black and blue filled circles respectively. The M_B associated with two apparent magnitude limited sample (17.5 appropriate for the HE survey, and 21.6 for the SDSS) are shown as a function of redshift.