Total fraction of obscured AGN with log N_H > 22 (left panel) and log N_H > 23 (right panel) vs. redshift measured in different X-ray samples (see labels) and compared with model curves of large-scale (ISM) plus small-scale (torus) obscuration. Only samples with median log L_X ≈ 44 have been considered here (see text for details). Curves have the same meaning as in Fig. 13. The model with γ = 2 and θ_torus = 60° (thick solid blue line) provides a good representation of the data.