B/p extent, at the end of the simulation run (t = 9 Gyr), computed for the thin and thick discs, as well as for the thin+thick case, for all the thin+thick models considered here. Left panels show the distribution for the rthickS models, whereas middle panels and right panels show the distribution for the rthickE and rthickG models, respectively. Thin disc b/ps always remain shorter than the thick disc b/ps. The errors on R_b/p are estimated by constructing a total of 5,000 realisations by resampling the entire population via a bootstrapping technique (for details, see Sect. 3.1.2).