The velocity shift as a function of L_Bol (a) and as a function of λ_Edd (b), for the WISSH sample (blue and red stars) compared to the PG QSOs from Baskin & Laor (2005) and Tang et al. (2012; greendiamonds), WLQs from Plotkin et al. (2015; orange circles), SDSS QSOs from Shen (2016) and Coatman et al. (2016;magenta squares and purple triangles), and HE QSOs from Sulentic et al. (2017, and reference therein). The L_Bol for the HE sample has been derived from L₅₁₀₀ applying a bolometric correction of 5.6, as suggested by Runnoe et al. (2012) for the luminosity range of the HE sample. c) Residuals plot of λ_Edd–L_Bol and –L_Bol relations. d) Residuals plot of L_Bol–λ_Edd and –λ_Edd relations. The black lines indicate the best linear fits to the data and the purple lines correspond to the 68% confidence interval.