Ratios between the predicted number of stars having Earths (N_★,mHC) of the two different prescriptions for P_E as in Fig. 1: GG GOOD and GG BAD cases, respectively. Results for M, FGK, and retired A are reported in the left, middle, and right panels, respectively. Ratios are computed as functions of the Galactocentric distance and Galactic time and all the displayed models consider the case 2 for the SN damage. Upper panels: reference models without stellar migration (ratio between model 7 and model 1 in Table 1). Lower panels: models with stellar migration and σ_RM = 3.5 (ratio between model 5 and model 3 in Table 1). In each panel the maximum value of the ratio is highlighted with an orange cross.