It is based on a three-part language question asked about all household members who are five years old or older.
Thus, languages which are widespread in certain areas of the country but not nationally get put together, even in block level data.
Several locally very well represented languages, such as Punjabi and Pennsylvania German, are collated into smaller groupings.
Native North American languages besides Navajo are also collated, though they are reported on several geographic levels in another data set.
Statistics on English-speaking ability and language spoken at home are used by the Justice Department in the implementation of the Voting Rights Act and to allocate funds for to schools for programs for English Language Learners.