Distribution of redshift, z, and intrinsic 2 − 10 keV X-ray luminosity, L_X, of the combined X-ray AGN sample with spectroscopic redshifts 0.3 ≤ z < 3 and L_X > 10⁴² erg s⁻¹. The top-left panel shows the redshift distribution for the obscuration samples selected via hydrogen column density, N_H, as indicated in the legend. The vertical red line indicates the low and high redshift bins. The top-right panel shows the distribution of L_X using the same line styles. The bottom panel shows the redshift against the intrinsic 2 − 10 keV X-ray luminosity; different colors and markers indicate the various surveys used.