Simulated average spectrum obtained by stacking synthetic spectra generated for each flux-resolved interval, incorporating observed trends in continuum slope, outflow velocity and the tentative ones in ionization and column density. The resulting stacked spectrum (black) is compared to absorbed power laws for each simulated flux interval (dashed gray). The absence of significant emission features in the stacked spectrum indicates that the emission observed in the actual average spectrum is unlikely to be an artifact of stacking variable flat spectra.