Mean C IV-Mg II velocity shift as a function of redshift from Mg II for our quasar sample (teal diamond), for the z > 5.8 dataset from Schindler et al. (2020), further divided into two redshift bins at z ≷ 6.35, and for a compilation of different samples collected in Meyer et al. (2019), for instance: SDSS DR7 and DR12, XQ-100 and z ∼ 6 − 7 quasars from Bosman et al. (2018) and Schneider et al. (2010), Shen et al. (2011), respectively. The x-axis bars mark the redshift range of each sample, while the errorbars on the y-axis report the standard deviation in each bin.