Histogram of heliocentric distances, D, for a) OCs and b) ECs, using a bin width of ΔD = 0.4 kpc and Poisson uncertainties. In each panel, the solid curve represents the fitted D-distribution Φ_D(D) from Eq. (8), with the completeness distance D_c as free parameter (see Eq. (9)); the dashed curve shows the fit with fixed D_c = 0 (see text for details). The best-fit parameters are given in Table 4.