Upper figure: comparison between the normalized MDF of stars (dotted) and GCs (full lines) in two distance regions of M 31. Each MDF is normalized to 1. Lower figure: logarithmic ratio between the normalized MDFs of clusters and stars as a function of [M/H] in bins of 0.6 at two distance regions of M 31. The weighted least square fit of (N_cl/N_stars) versus [M/H] for the inner and outer regions are shown by dotted red and blue lines respectively. The black line is the fit to all data and has a slope of −0.69 ± 0.27.