Ratio of SFR and CO-inferred H₂ mass vs. relative metallicity as described in the text, including our data and data from the literature (COLDGASS: Schruba et al. 2012; Bothwell et al. 2014). As in previous figures, the open triangles for Schruba et al. (2012) correspond to their compilation of data from the literature and the filled ones to their metal-poor dwarf observations. Following Krumholz et al. (2011), here M_H2 is inferred with a constant α_CO = 4.4 M_⊙ (K km s^-1 pc²)^-1, as described in the text. Also shown are the predictions by Krumholz et al. (2011), showing three values for total gas surface density, Σ_gas: 5 M_⊙ pc^-2, 20 M_⊙ pc^-2, and 80 M_⊙ pc^-2 indicated by dashed, dotted, and solid lines, respectively. Total gas corresponds to red, purple to H₂, and blue to CO.