Observed stellar [Mg/M] vs. [M/H] abundance ratios from MWM DR19 (Meszaros et al., in prep.) for the six bins of different Galactocentric distances considered here. The regions plotted from the top are all 2-kpc-wide, and are centered at R₁ = 4 kpc, R₂ = 6 kpc, R₃ = 8 kpc, R₄ = 10 kpc, R₅ = 12 kpc, and R₆ = 14 kpc, respectively. The sample size in the i-th region is denoted by N_i. Red and blue squares represent the binned distributions of the high-Mg and low-Mg sequences, respectively. Details on the data selection are reported in the text.