Comparison of the observed metallicity distribution function of the M31 bulge from Sarajedini & Jablonka (2005) (black) with that predicted by our chemical evolution models for a variable IMF scenario, adopting yields from R10 and F04, shown as dashed red and hatched light-blue histograms, respectively, and an outside-in model with yields from F04 (dot-dashed green histogram). Slight shifts have been applied to the histograms for display purposes.