5 GHz radio power against redshift for the 138 sources from the PS sample for which redshift data is available (black circles). The green triangles, blue squares, and orange diamonds represent the PS samples of O’Dea (1998), Snellen et al. (1998), and Callingham et al. (2017), respectively. The dashed grey line corresponds to the 5 GHz luminosity limit for a source that has a peak flux of 44 mJy at 144 MHz, corresponding to the 90% completeness limit of the PS source selection. To compute this 5 GHz luminosity limit, a median spectral index of −0.87, corresponding to the 90% limit of α_high, was used.