Escape fraction vs. IFP for QSOs at z > 3.80. The gray points show the escape fractions calculated with the ionizing window 892−905 Å rest frame, and the orange points represent the escape fractions with the reduced ionizing window 898−905 Å rest frame. The black filled square represents the mean f_esc in IFP bins of 30 pMpc (the open square is the mean of f_esc in IFP bins containing fewer than ten sources). The vertical bars are the error on the mean in each IFP bin. QSOs with z <  3.8 have been excluded here to avoid possible biases due to their underestimated IFP, as discussed in Sect. 6.1.1.