Fractions of log(L_2 − 10)∼44 obscured AGN as a function of redshift. The navy circles are the observed fractions, while the light blue squares are those obtained once corrected for the presence of the survey sky coverage. The second set of points is shifted by 0.05 on the z-axis for visual clarity. The solid magenta line represents the predictions from the Gilli et al. (2007) model for the intrinsic obscured fraction; the dashed purple line is the prediction for the observed fraction once the sky coverage is taken into account. Left: obscured fraction derived using N_H > 10²² cm⁻² as the threshold (f₂₂). Right: obscured fraction derived using N_H > 10²³ cm⁻² as the threshold (f₂₃).