Distribution of cluster distances with mass. The clusters located inside and outside the magnitude-dependent completeness limits computed in Eq. (7) are shown with black and light blue dots, respectively. The single completeness limit for the MWSC sample is given by the horizontal red line. A vertical yellow stripe is given for illustration and indicates an arbitrary log m_t-box with clusters of the two kinds falling in it. Red crosses show ‘central’ (R ≤ 3 kpc) clusters excluded from further consideration.