In naturally occurring text, the more frequent sense for the two-sense distinction is reported to occur 92% of the time on average; this result has been found both on the CACM collection and on the WordNet SEMCOR sensetagged corpus (Sanderson & van Rijsbergen, 1999).
the challenge for WSD programs is to work on the harder cases, and the artificially constructed SENSE-VAL1 corpus has more evenly distributed senses (Gaustad, 2001).