Ring radius derived for each KI target (filled circles) after the correction for host galaxy and unresolved AD component, plotted against UV luminosity, or scaled V-band luminosity (extrapolated from the WFCAM SED; see Sect. 4.1). The reverberation radii against the same scaled V-band luminosity (Suganuma et al. 2006, and references therein) are also indicated by gray plus signs in addition to their fit (dotted line).