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Radiative efficiency is an important physical parameter that describes thefraction of accretion material converted to radiative energy for accretion ontomassive black holes (MBHs). With the simplest So{\l}tan argument, the radiativeefficiency of MBHs can be estimated by matching the mass density of MBHs in thelocal universe to the accreted mass density by MBHs during AGN/QSO phases. Inthis paper, we estimate the local MBH mass density through a combination ofvarious determinations of the correlations between the masses of MBHs and theproperties of MBH host galaxies, with the distribution functions of thosegalaxy properties. We also estimate the total energy density radiated by AGNsand QSOs by using various AGN/QSO X-ray luminosity functions in the literature.We then obtain several hundred estimates of the mean radiative efficiency ofAGNs/QSOs. Under the assumption that those estimates are independent of eachother and free of systematic effects, we apply the median statistics asdescribed by Gott et al.\cite{got01} and find the mean radiative efficiency ofAGNs/QSOs is $\epsilon=0.105^{+0.006}_{-0.008}$, which is consistent with thecanonical value $\sim0.1$. Considering that about $20\%$ Compton-thick objectsmay be missed from current available X-ray surveys, the true mean radiativeefficiency may be actually $\sim 0.12$.

On the Mean Radiative Efficiency of Accreting Massive Black Holes in AGNs And QSOs