Top: mean number of satellites around an MW-mass halo as a function of the minimum satellite absolute magnitude. Solid and dotted–dashed lines are the predictions from Dooley et al. (2017b), based on Garrison-Kimmel et al. (2017, GK2017+reion) and Brook et al. (2014, Brook2014+reion), respectively. The data for the observed luminosity functions come from the Crnojević et al. compilation. The regions where the Cen A and M81 luminosity functions become incomplete are shown with hollow symbols and dashed lines. We mark our ≳90% completeness limit for each distance fiducial (cyan: 1.5 Mpc, blue: 3.5 Mpc, magenta: 5 Mpc). Bottom: predicted mean number of satellites around an isolated low-mass host as a function of the minimum satellite absolute magnitude from Dooley et al. (2017a; black: LMC-mass host, gray: SMC-mass host).