The postion of inflected verbs in early Yiddish varies between second position and positions later in the clause. Standard distributional tests establish that this reflects variation in the underlying position of infl, and that Yiddish phrase structure changed from infl-final to infl-medial. Based on clauses containing the relevant structural diagnostics, we can estimate the rate of this change. We cannot, however, determine the phrase structure of structurally ambiguous clauses (i.e., those superficially consistent with either of the phrase structures) with certainty. Nevertheless, we can use quantitative methods to estimate the likelihood of such clauses being infl-medial, and we can then use these likelihoods to provide an additional estimate of the rate of the change. Comparing both estimates reveals that they do not differ significantly. The implications of this result are briefly examined in conclusion.