Binary classification into quasar and non-quasar giants based on SDSS DR12 host spectra, for 5 redshift intervals. We selected all giants with definite hosts within the SDSS-covered sky patch bounded by right ascensions 120° and 250°, and declinations 27° and 62°. As redshift increases, the fraction of hosts with a known spectral class decreases (grey bars, with the absolute number of such hosts in black), whilst the fraction of quasar identifications increases (blue bars and white percentages).