We analyze 1049 QSOs and AGNs from the Large Bright QSO Survey to produce new constraints on the shape and evolutionary behavior of the bright end of the QSO luminosity function. The data represent more than an order of magnitude improvement for redshifts 0.2 < z < 3, and absolute magnitudes corresponding to apparent magnitudes 16.5 < m_bJ_, < 18.85. The results are poorly described by the predictions of a model in which a two power-law luminosity function of constant shape evolves strongly until redshift z~2, in such a way as to mimic the effect of pure- luminosity evolution. In the Large Bright QSO Survey sample the shape of the luminosity function changes systematically as a function of redshift, becoming steeper at larger redshifts. Compared to current models, the rate of evolution is less rapid over the redshift range 0.2 < z < 2, but continues, at a significantly reduced rate, until at least redshift z~3. A significant revision of the presently accepted model for the evolution of the QSO population is indicated.
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Hewett et al. (1993) studied this question.