Obscured fraction with log N_H ≥ 23 vs. redshift. Our results are shown as the purple shaded regions that represent the 68% and 95% confidence intervals of the best-fitting absorption function. Also shown are the extrapolation (grey shaded regions) of the absorption function below and above the redshift range of our analysis. For reference, shown are the results of Liu et al. (2017), Vito et al. (2018), Vijarnwannaluk et al. (2022), and Signorini et al. (2023), which span a wide range of redshifts. The luminosity ranges used in these studies are given in brackets (see legend in inset). The lines are the predictions of the obscuration fraction originated on both ISM and torus components (Gilli et al. 2022) for different values of the obscuration evolutionary factor, δ.