Evolution of the orbital period derivative Ṗ/P of our model d2ns0 shown in Fig. 9 as given by the numerical simulation (orange line), together with our analytic estimate for the same model (see text; yellow line). Overplotted are the empirical decay rates of ten SGXBs as inferred by Falanga et al. (2015), who give six measured values with 1σ error bars (blue dots; for most of these, the error bar is smaller than the size of the dot) and four upper limits (blue arrows). We note that the time axis has no meaning for the period derivatives of the observed sources.