Mean score of human judgments and $M0.52$ score for each system in domains (NF = Native Formal, NWI = Native Web Informal, R = Romani, SL = Second Learners, Σ = whole dataset). All results in the whole dataset (the Σ column) are statistically significant with p-value <0.001, except for the AG finetuned and Joint GEC+NMT systems, where the p-value is less than 6.2% for $M0.52$ score and less than 4.3% for human score, using the Monte Carlo permutation test with 10M samples and probability of error at most 10⁻⁶ (Fay and Follmann, 2002; Gandy, 2009).