Average transmitted flux in the rest-frame region 1041 Å < λ_RF,QSO < 1185 Å of the quasar spectra, as a function of the Lyα redshift, compared to the average cosmic value measured by Becker et al. (2013). Shown are the mean (purple) and median (violet) stacked spectra in three Lyα redshift intervals within 2.5 ≲ z ≲ 4.5. The uncertainties reproduce the standard deviation in each bin. In the background, there is the average transmission of individual spectra (in gray).