THE EVOLUTION OF QSOS

I review the most recent results on the cosmological evolution of the QSO population. I focus on the ensemble average properties of the QSO population including their space density/luminosity, clustering, galaxy environment and host galaxies. I show that the cosmological evolution of QSOs closely parallels that of galaxies and that many of the properties of QSOs are consistent with a picture in which QSO activity may be linked to the formation of galaxy spheroidal components in the early Universe.