The redshift and temperature distributions of the low- and high-redshift cluster samples used in this work. The solid grey marks the low-redshift sample (z < 0.5) and the shading with diagonal lines marks the high-redshift sample (z > 0.5). Note that the high-redshift sample (T_median = 4.5 keV) contains more high-temperature clusters than the low-redshift sample (T_median = 3.0 keV).