To conclude, both the DBE and DSG model are able to detect directed drifts even in the 1 % subset of the NYT corpus, while the ISG can not.
the drift distributions of the DBE and DSG models have a much shorter shorter tail on the 1 % subset than on the 10 % subset: they are not able to discriminate very high drifts from the rest of the words in extreme scarcity situation.