small, not allowing us to reach a firm conclusion on the variation of the iron K$\alpha$ $EW$ with the luminosity. Possible evidence of a flattening of the X-ray Baldwin effect in the quasar regime has been recently found by @Krumpe:2010vn.

On the differences between X-ray and IR half-opening angle-luminosity relationships
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The main difference between the different $\theta_{\mathrm{OA}}-L_{\mathrm{X}}$ relationships we used is that those obtained in the X-rays are based on direct observations of the absorbing material in the line of sight, while the one of @Maiolino:2007bh is extrapolated from the ratio of the thermal infrared emission to the primary AGN continuum. The $\theta_{\mathrm{OA}}-L_{\lambda}(5100\AA)$ relationship obtained by @Maiolino:2007bh was converted in $\theta_{\mathrm{OA}}-L_{\mathrm{X}}$ using the $L_{\,2\rm\,keV}-L{\lambda}(2500\AA)$ relation obtained by @Steffen:2006uq, and then converted in the $L_{\mathrm{X}}-L_{\lambda}(5100\AA)$ relation assuming the optical-UV spectral slope obtained by @Vanden-Berk:2001kx. All this is likely to introduce some error in the $\theta_{\mathrm{OA}}-L_{\mathrm{X}}$ obtained by their IR work. It has been argued by @Maiolino:2007bh that the larger normalization of the $\theta_{\mathrm{OA}}-L_{\mathrm{X}}$ relation they found is related to the fact that medium X-ray surveys such as that of @Hasinger:2008ve are likely to miss a certain fraction of heavily obscured objects, which can instead be detected in the IR. This 