Ethnicity estimates are generally considered to be accurate at continental level, but less so the more precise they claim to be. Smaller percentages should be treated with greater suspicion.
Ancestry's "DNA Communities" is a rather misleading term. Whilst the more general ethnicity allocations are derived from DNA matching across reference populations, the DNA Communities are not directly calculated from your DNA. They are inferred by a computational algorithm from the locations entered in the family trees of members with whom you have matches, so similar to the way that the Thrulines algorithm works, and therefore just as susceptible to inaccuracy dependent upon the accuracy of other family trees and other assumptions.
I have mentioned here before that my brother and I are both attributed by Ancestry to two communities in the United States, including Ohio, Indiana and Eastern Kentucky. Our direct Ancestors have never been anywhere near that region, nor do any of them originate from the USA. But our maternal GGF whose family origins are Welsh, had several wives before marrying our GGM. His wives were all from English families, but several of his sons from his first marriage emigrated to the USA in the late 19th century, where there are now numerous descendants who have taken DNA tests with Ancestry and created family trees, all half-cousins at various degrees of separation with whom we share DNA Matches through our GGF alone. As a result, Ancestry insists that we are partly of North American origin! ("Generally accurate at continental level" ?)
