Relative constraining power of various data on Model II. While the global constraints on the evolution of the neutral fraction and τ (gray and orange) produce a degenerate surface, the fit is constrained by the Steidel et al. (2018) measurement (purple) of ﹩{f}_{\mathrm{esc}}﹩ that we adopt by assuming the ﹩{{\rm{\Sigma }}}_{\mathrm{SFR}}﹩ for their sample follows the average relation in Figure 5. We adopt uniform priors of 0 to 5 for a and −5 to 5 for b, allowing for a ﹩{{\rm{\Sigma }}}_{\mathrm{SFR}}﹩–﹩{f}_{\mathrm{esc}}﹩anti-correlation that is rejected by the evidence. The posteriors are instructive for future studies: complex models of ﹩{f}_{\mathrm{esc}}﹩ only constrained by global quantities like ﹩{\bar{x}}_{{\rm{H}}{\rm{I}}}﹩ and τ result in degenerate parameters (gray and orange) and require measurements like Steidel et al. (2018; purple) that directly link ﹩{f}_{\mathrm{esc}}﹩ to galaxy properties.