Hyatt recorded thousands of interviews in the Jim Crow South as a white clergyman paying Black practitioners to describe a practice that had been criminalised and ridiculed. The transcripts record what was said. They cannot record what was not said, what was simplified for a paying outsider, or what was offered in place of something withheld. Every quantitative claim drawn from the collection, about regional distribution, about the frequency of a given practice, about what conjure was for, inherits this and it is rarely stated.
What would resolve this Comparison of Hyatt's material against independently gathered testimony from the same communities and period, including Hurston's, the Federal Writers' Project narratives, and community-held family records, looking systematically for what appears in one and not the other. Oral history with descendants of identified informants, where the identification can be made, would test it directly. The question is answerable in principle and has not been pursued at scale.
OpenAfrican American folklore studies, oral history and the historiography of ethnographic fieldworkYvonne P. Chireau, Black Magic: Religion and the African American Conjuring Tradition