Left (from top to bottom): model profiles of stars, gas, SFR and molecular gas fraction f_Mol at 4, 8 (thin curves) and 12 Gyr (thick curve). The curve at 12 Gyr is compared to observational data for the present-day profiles of the correspoding quantities (shaded aereas for the stars, gas and f_Mol and points with error bars for the SFR); data sources are provided in KPA15. Right (from top to bottom): infall timescales, infall rates, velocity profiles of radial inflow (positive values towards the Galactic centre), ratio of SNIa/CCSN; in all panels but the top one, the three curves correspond to 4, 8 and 12 Gyr (thickest curve).