A tribal block group (BG) is a cluster of census blocks having the same first digit of their four-digit identifying numbers and are within a single tribal census tract. The optimum size for a tribal BG is 1,000 people; it must contain a minimum of 300 people. The difference between a tribal BG and a nontribal BG is in the hierarchical presentation of the data. A tribal BG is part of the American Indian hierarchy; that is, the tribal BG is within a tribal census tract that is within a federally recognized American Indian reservation and/or off-reservation trust land.
