The estimates of the ratios for the two S[+R] rules are obtained by counting the proportion of subject relatives among all relatives in the Treebank's parsed Brown corpus 7 .
(3) relative clauses in the Treebank are analyzed as NP → NP SBAR (rule 1) SBAR → WHNP S (rule 2) where the S contains a trace *T* coindexed with the WHNP.