Though syntactic parsers for English are reported to have accuracies over 90% on the Wall Street Journal (WSJ) section of the Penn Treebank (PTB) (McDonald et al., 2005;Sagae and Lavie, 2006;Huang, 2008;Carreras et al., 2008), broad-coverage parsing is still far from being a solved problem.
metrics like attachment score for dependency parsers (Buchholz and Marsi, 2006) and Parseval for constituency parsers (Black et al., 1991) suffer from being an average over a highly skewed distribution of different grammatical constructions.