BAL quasar fraction as a function of Log Eddington ratio. The error bars and shaded regions represent binomial errors. The red circles correspond to the 1.88 <  z <  2.44 sample with Mg II-based black hole masses, while the black triangles represent the broader 1.5 <  z <  4.5 sample. The blue dashed lines mark one standard deviation from the mean Log Eddington ratio, defining the low and high Eddington ratio regions.