BFs of CE and SMT models with respect to the reference model with α_CE = 1.0 and Eddington-limited accretion efficiency as a function of sample size. The initial sample contains 38 GW events of GWTC-2 and exclude GW170729, GW190413_134308, GW190519_153544, GW190521, GW190602_175927, GW190620_030421, GW190701_203306, GW190706_222641, GW190929_012149. At each iteration the event with lowest likelihood with respect to the reference model is removed and indicated on the horizontal axis until 20 events are removed. By definition the BF of the model with α_CE = 1.0 is equal to 1. The data show moderate to strong support for the models with low CE efficiency, α_CE < 1.0. This result is robust because the BFs show a constant behaviour as a function of sample size.