Mass density of SMBHs (solid lines), active SMBHs (dashed lines), and type-1 AGN (dotted lines) for the three values of the radiative efficiency indicated in the plot. The thin blue solid line corresponds to results from Ueda et al. (2014). If ϵ = 0.1 or 0.07, the evolution of the mass density is relatively modest. On the contrary, if ϵ = 0.05, the mass density at z = 4 is two orders of magnitude lower than the local one. The AGN mass density has similar evolution for the three cases, with a peak at approximately z = 0.5–1.5.