However, since the causative is a transitive use, and the transitive use of unergatives is expected to be rare (see above), we do not expect unergatives to exhibit a high degree of detectable overlap in a corpus.
this overlap of subjects and objects should primarily distinguish unaccusatives (predicted to have high overlap of subjects and objects) from the other two classes (each of which is predicted to have low [detectable] overlap of subjects and objects).