Dependence of the CEMP fraction (upper panel) and the fraction f_NEMP of NEMP stars among all CEMP+NEMP stars (lower panel) for our default model A, as a function of the median mass M_med and dispersion σ_M for a log-normal IMF. Contours in the upper panel correspond to CEMP fractions between 10% and 25%, which spans the range of observed values. The solid contours in the lower panel correspond to the 90%, 99% and 99.9% confidence upper limits on f_NEMP in the range  −2.8 ≤  [Fe/H]  ≤  −1.8 and log g ≤ 4, while the dashed line shows the 99% upper limit on f_CNEMP (see Table 2). The star symbols labelled 4, 5 and 6 indicate the IMFs of Miller & Scalo (1979), Lucatello et al. (2005a) and Komiya et al. (2007).