Luminosity-redshift diagram for the XMM-LSS, XMM-CDFS, and XMM-COSMOS surveys. The contours are logarithmically scaled and show the fraction of objects with z and L inside the contour (levels at 97%, 94.8%, 90%, 83%, 70%, and 48% from outermost to innermost). The data points show the objects outside the lowest contour. At z> 0.5, the XMM-CDFS systematically probes AGN that are fainter by up to one order of magnitude. Observed luminosities, corrected only for Galactic absorption, are shown.