Stacked PDFs of sources with true N_H in a single N_H bin in four different redshift subsamples (top four panels) and in four S/N subsamples (bottom four panels). The orange area shows the true N_H (amplitude fixed to 1 for clarity), and the black line shows the stacked PDF. We note that sources with negative S/N are formally detected by ewavelet, since the background is estimated differently. All distributions are normalized to unit area.