EMRI-to-plunge ratio as a function of the sBH number fraction, assuming sBHs of mass m _• = 10M _⊙ (blue line) and m _• = 30M _⊙ (red line), as calculated from Equations (20) and (21). The dashed–dotted lines mark the critical number density, ﹩{f}_{\bullet }^{c}﹩ (Equation (12)), for each sBH mass, with respective colors, and the dashed lines present the ratio in the limiting cases of scarce (﹩{{\rm{f}}}_{\bullet }\ll {f}_{\bullet }^{c}﹩) and abundant (﹩{{\rm{f}}}_{\bullet }\gg {f}_{\bullet }^{c}﹩) sBH populations (Equations (22) and (23)), respectively.