Error-coded corpora are effective training and evaluation data for targeted error correction, and statistical classifiers have been developed to handle errors involving closed-class words (Rozovskaya and Roth, 2014).
the 2014 CoNLL shared task engendered a sea change in GEC: in this shared task, systems needed to correct all errors in a sentence, of all error types, including ones more stylistic in nature (Ng et al., 2014).