Top panel: type 1 AGN photon index versus redshift (left) and luminosity (right). The size of the circles indicates the size of the errors on the photon index. The horizontal dotted line corresponds to the average photon index for the whole sample. Bottom panel: type 1 AGN average photon index versus redshift (left) and luminosity (right) for the luminosity and redshift bins. The error bars correspond to the mean error at 1σ confidence level, whereas the dashed lines mark the values for the intrinsic dispersion at each bin.