Radiative efficiency is an important physical parameter that describes the fraction of accretion material converted to radiative energy for accretion onto massive black holes ( MBHs ) .
With the simplest Sołtan argument , the radiative efficiency of MBHs can be estimated by matching the mass density of MBHs in the local universe to the accreted mass density by MBHs during AGN/QSO phases .
In this paper , we estimate the local MBH mass density through a combination of various determinations of the correlations between the masses of MBHs and the properties of MBH host galaxies , with the distribution functions of those galaxy properties .
We also estimate the total energy density radiated by AGNs and QSOs by using various AGN/QSO X-ray luminosity functions in the literature .
We then obtain several hundred estimates of the mean radiative efficiency of AGNs/QSOs .
Under the assumption that those estimates are independent of each other and free of systematic effects , we apply the median statistics as described by Gott et al . [ 1 ] and find the mean radiative efficiency of AGNs/QSOs is \epsilon = 0.105 ^ { +0.006 } _ { -0.008 } , which is consistent with the canonical value \sim 0.1 .
Considering that about 20 \% Compton-thick objects may be missed from current available X-ray surveys , the true mean radiative efficiency may be actually \sim 0.12 .