Left panel: probability density distribution of the SMBHB candidates from the E12 sample, ﹩\rho (\tilde{a},q,z)﹩, integrated over redshift. Middle panel: probability of detecting a SMBHB with the radial component of orbital velocity greater than vlim = 350 km s−1. The red dashed line marks the Pv = 0.1 contour. Right panel: the probability density distribution of the inferred SMBHBs population after accounting for the selection effects, ﹩\rho (\tilde{a},q,z)/{P}_{\mathrm{bias}}﹩. The probability density in the grayed-out region is set to zero (see Section 2.3).