SFR_NORM over L_X (in logarithmic scale) as a function of redshift. Our results are divided into three bins (blue circles) of equal size with uncertainties calculated with the bootstrap resampling method. We also plot the data points from X-ray-selected samples with a variety of luminosity and redshift ranges as shown in the legend. The dotted line shows the best linear-fit function: y = 0.0018 ± 0.0005 × x − 0.0002 ± 0.0013.