Clefts are understood as biclausal structures involving the movement of a clefted constituent from a lower clause, where it is generated, to a higher clause, where it is interpreted. Though both grammatical, subject and object clefts show signs of different acceptability in experimental settings. This degradation is ascribed to the fact that the object needs to cross an intervening subject, thus triggering intervention effects. In this paper, we show that intervention effects are also present in grammatical configurations, and give rise to lower-than-expected frequencies. Based on sets of features that play a role in the syntactic computation of locality, we compare the theoretically expected and the actually observed counts of features in a corpus of thirteen syntactically annotated treebanks for three languages (English, French, Italian). We find the quantitative effects predicted by the theory of intervention locality: object clefts are less frequent than expected in intervention configuration, while subject clefts are roughly as frequent as expected. We also find that the size of the effect is proportional to the number of features that give rise to the intervention effect. These results provide a three-fold contribution. First, they extend the empirical evidence in favour of the feature-based intervention theory of locality. Second, they provide theory-driven quantitative evidence, thus extending in a novel way the sources of evidence used to adjudicate theories. Finally, the paper provides a blueprint for future theory-driven quantitative investigations.