Normalised molecular gas mass fraction μ_mol  ≡  M_gas/ℳ as a function of the normalised SFR. The symbols are defined as in Fig. 13. The black solid curve and grey area represent the values predicted by the 2-SFM framework described in Sargent et al. (2014). Sources with ℳ >  10¹¹ M_⊙ are shown with magenta large squares. The grey area shows the expected 1σ scatter around the average molecular gas mass fraction.