Temporal variation of b/p extent, R_b/p, calculated using thin-, thick-disc, and thin+thick disc particles for model rthickE0.5. The b/p extent increases by a factor of ∼2 over the total simulation runtime. At t = 9 Gyr, the thick-disc b/p remains a bit larger than the thin disc b/p. The errors on R_b/p are estimated by constructing a total of 5000 realisations by resampling the entire population via a bootstrapping technique (for details, see text).