The people of Laos are often categorised by their distribution by elevation: (lowlands, midlands and upper high lands) as this somewhat correlates with ethnic groupings. More than half of the nation's population is ethnic Lao—the principal lowland inhabitants, and the politically and culturally dominant people of Laos. The Lao belong to the Tai linguistic group who began migrating south from China in the first millennium CE. Ten percent belong to other "lowland" groups, which together with the Lao people make up the Lao Loum (lowland people).