PhSR as a function of redshift. The top hat function plotted in orange is the selection function holding for WPS_spec. The shaded area and blue points refer to the observational estimate (using the 20 K-sample) of the success rate of our photometric redshift selection. The continuous green (dashed red) line shows analytical predictions of PhSR for the sample of targets within WPS_spec that are brighter (fainter) than I_AB = 22.5.