The ER metric, which was derived from counts of errors detected using e-rater R , is nearly as good as the state-of-the-art RBM (GLEU) and the interpolation of these metrics has the strongest reported correlation with the human ranking (ρ = 0.885, r = 0.867).
since e-rater R is not widely available to researchers, we also tested a metric using Language Tool, which does nearly as well when interpolated with GLEU (ρ = 0.857, r = 0.867).