  Notional anaphors are pronouns which disagree with their antecedents'
grammatical categories for notional reasons, such as plural to singular
agreement in: 'the government ... they'. Since such cases are rare and conflict
with evidence from strictly agreeing cases ('the government ... it'), they
present a substantial challenge to both coreference resolution and referring
expression generation. Using the OntoNotes corpus, this paper takes an ensemble
approach to predicting English notional anaphora in context on the basis of the
largest empirical data to date. In addition to state of the art prediction
accuracy, the results suggest that theoretical approaches positing a plural
construal at the antecedent's utterance are insufficient, and that
circumstances at the anaphor's utterance location, as well as global factors
such as genre, have a strong effect on the choice of referring expression.
