 Just as a central issue concerning acceptability judgment data concerns its reliability as evidence for empirical generalizations about languages or idiolects, a central question concerning the collection of corpus data concerns whether or not it is representative of the language variety it purports to represent. Some linguists make the criterion of representativeness definitional: they call a collection of samples of language use a corpus only if it has been carefully balanced between different genres (conversation, informal writing, journalism, literature, etc.), regional varieties, or whatever.