Luminosity dependence of the AGN narrow-line emission strength and IR excess emission. For each quasar, we have interpolated and smoothed the observed SEDs, subtracted a WDD AGN template with the normalization at rest-frame 3.3 μm, and computed the relative excess luminosity at 5–25 μm as (L _obs − L _WDD)/L _WDD. The red lines show the linear regressions of the data points with the fitted relations reported in the top-right corner of each panel.