Correlations between the surface density (left) and the volume density (right) of the gas and the SFR in the MW, colour-coded according to the Galactocentric radius. The squares indicate measurements for R ≤ R_⊙ from Marasco et al. (2017), while the circles are for R >  R_⊙ from Binney & Merrifield (1998), Nakanishi & Sofue (2003, 2006), and Levine et al. (2006) (see text). The grey points are the corresponding quantites for the sample of 12 nearby disc galaxies (see Figs. 5 and 6 in B19 for the whole range of densities). The solid line in the right panel is the VSF law from B19 with its intrinsic scatter (red band).