Distribution of spectroscopic redshifts for confirmed quasars in the sample (solid line). The dashed line shows the photometric redshift distribution of the spectroscopically-confirmed quasars. The photometric redshifts are only as accurate as the size of the redshift bins that can be used to define the color–redshift relation, which coarsely quantizes the z _phot distribution. Gray squares indicate the fraction of photo- z's that are correct to within ±0.3 for each z _phot bin. These are most accurate where the most data exist (1 < z < 2).