"Pointer-Generator-all" has 99.6% of unigrams, 95.2% bigrams, and 87.2% trigrams contained in the source documents (DUC-04).
the ratios for human summaries are 85.2%, 41.6% and 17.1%, and for "AMRSumm-Clst" the ratios are 84.6%, 31.3% and 8.4% respectively.