These two families are confined to the Center and the South. The Mon-Khmer, which form part of the Austronesian family, number 1.7 million (2.6% of the country’s population). They can be divided into two spatially distinct subgroups on the basis of their way of life. The Montangards, who practice swidden agriculture, live on the plateaus where they comprise 17-23% of the population. Outside the plateaus, they are found in Quang Ngai, Song Be, and—more recently—in the border provinces of Quang Nam-Da Nang and Dong Nai where their increase has been greatest. The Khmer minority, well settled in the Mekong Delta long before the Vietnamese arrived there, practice wet rice cultivation. Today they represent 7-14% of the population in the southern part of the delta.
The Austronesians are a much smaller ethno-linguistic family numbering only 0.6 million (1.0% of the population). Like the Mon-Khmer, they are also divided into two sub-groups. Those living on the plateaus, practice swidden agriculture. Their number, which decreases from north to south, has increased fastest in Lam Dong. The Chams, who grow rice on the plains, used to control the middle of the Central region. As the Vietnamese gradually pushed south, however, the Cham retreated to the provinces in the south-central region where they are now mainly concentrated.