Dannenberg, Clare J. “Grammatical and phonological manifestations of null copula in a tri-ethnic contact situation.” Journal of English Linguistics 27.1 (December 1999): 356-370.
Studies the use of null copula (examples: “she ugly.” or “you ugly.”) among African American, Anglo American, and Lumbee Indian speakers in Robeson County, North Carolina. The data was derived from 39 tape-recorded sociolinguistic interviews, evenly distributed among the three ethnic groups, which were recorded as part of the North Carolina Language and Life Project. The VARBRUL computer program was used to analyze the 1,851 tokens of full, contracted, and null copula for is and are. The author found that African American speakers have a much higher overall incidence of null copula (43%) that the other two groups. Incidence among Lumbee and Anglo American speakers is about the same. She notes that, unlike other linguistic features such as perfective I'm and finite be(s), null copula is not ethnically marked for the Lumbee.