In a country as ethnically diverse as Laos, the distribution of the population by ethno linguistic families and ethnic groups is a key to understanding the maps. The 1995 census provides this information at district level. The table opposite recognizes five ethno linguistic families according to their scientific classification, which is rare for a country of this size. Of the 47 ethnic groups recorded in the census, this table includes only those that number over 25,000 members, with the exception of the Hor, who, although less numerous, represent the fifth ethnolinguistic family.

The Tai-Kadai family, designated by the term Lao Loum (i.e. Lao of the plains and valleys), make up two- thirds of the country's population. This family includes the Lao—who account for just over half of the total—and only five other ethnic groups. After the Lao, the term Phutai covers a number of smaller groups from this family, such as the White Tai, Black Tai, Red Tai and Tai Phouan, which together account for 10% of the total population and 16% of the Tai-Kadai.

The second ethnolinguistic family, the Austro- Asiatics, 23% of the total population, consists of two branches, distinguished in the table: the dominant Mon-Khmer and the small minority of Viet-Muong in Laos. This family comprises 30 ethnic groups, i.e. 64% of those listed in the census: some of these groups have only a few thousand members, while the dominant group—the Khmu—comprises half a million people. This family is designated by the term Lao Theung (Lao of the slopes), because these groups were driven off the plains with the arrival of the Lao.

The next two families, the Miao-Yao (called Hmong-Yao in Laos) and the Tibeto-Burmans were only able to settle on the mountain peaks when they arrived in the 19th century, which explains why they are both referred to by the same term Lao Soung (Lao of the summits). They represent respectively 7.4% and 2.7% of the population. The Hmong, with 3.15,000 members, is the fourth largest ethnic group, behind the Lao, the Khmu and the Phutai. The last group, the Hor, belongs to the Sino- Tibetan ethnolinguistic family and numbers fewer than 10,000 persons.

Another key to the distribution of the population is the differentiation between urban and rural populations, a source of numerous errors of interpretation. The population of Vientiane city is often considered as the 524,000 inhabitants of the municipality, which is composed of nine districts. However, only four of these are urbanized and total  266,500  inhabitants,  of which  only  233,500  are recorded as town-dwellers in the census. There are also three peri-urban districts, where town-dwellers represent between a third and half of the population, and two rural districts. Altogether, the urbanized population of Vientiane municipality totals 331,000.

The census definition of the urbanized population takes into account only the population of the urban villages, characteristic of urbanization in this part of Asia. To qualify as "urban", a village must meet three of the following five conditions: it must be located within the vicinity of the administrative capital of the province or district; the majority of households must have electricity and piped water; it must have a market; and it must be accessible to motorized vehicles.

This definition is extremely broad, since the last two criteria apply to any village center located along a road, and "within the vicinity" remains imprecise. The Housing and Urban Planning Department requires other criteria: residential density of more than 30 persons per hectare; a population of more than 2,000; and the availability of other services beyond a local market. According to these requirements, the population of the capital comes down from 233,500 to 166,500. It would be useful to harmonize the definitions to allow more accurate analysis.

The structure of housing also sheds light on this issue. The 1995 census contains information on the size and tenure status of housing, construction materials, water and electricity supply, source of energy used for cooking, and type of sanitation. On the basis of construction materials, for example, a distinction can be made between traditional rural  dwellings in  wood or bamboo,  and permanent dwellings—Chinese compartments typical of Asian cities, villas and apartment buildings.

The information from the census, processed at district  level  and  compared  with  the  rural-urban differentiation, makes it possible to analyze urbanization in Laos for the first time. This analysis, beginning in this chapter, continues, wherever possible, throughout the atlas. It culminates in the conclusion with a typology of the towns and a hierarchy of the urban network, which are essential for designing a balanced strategy of territorial development.

Ethnolinguistic families: Tai-Kadai and Austro-Asiatics

The Tai-Kadai family accounts for over 84% of the population along a continuous ribbon that runs through the districts bordering the Mekong from Paklai (Xayabury) to the Cambodian border. The Lao prevail over the other ethnic groups in the Tai-Kadai family from Luangphrabang and this belt widens along the river. The Tai-Kadai make up between 64% and 84% of the population around the provincial border separating Khammouane and Savannakhet, and along the axis between Vientiane and Xamneua. Therefore, Huaphanh and Xiengkhuang provinces cannot be considered as a periphery like the other mountainous provinces of the North and South. A number of maps in the atlas confirm this observation. The Phutai are concentrated in the eastern half of the provinces lying between the Mekong and the Vietnamese border in the Center.

The Mon-Khmer branch of the Austro-Asiatic family is concentrated in two nuclei of settlement. In the North, the Khmu, centred on the provinces of Oudomxay and Luang phrabang, account for between 43% and 73% of the population. They continue into the neighboring provinces and are extended by the Thin in northern Xayabury. The other ethnic groups in this family account for over three-quarters of the population in the districts along the  Vietnamese  border  in  the  South.  Unlike  the homogeneous Khmu, these groups form a mosaic, reflecting multi-ethnic areas. The largest is the Katang (95,000 persons) in Savannakhet province. The Taoey and Xouay are concentrated in Saravane province, the Talieng in Sekong province, and the Laven on the border between Champassack and Attapeu provinces.

The few Viet-Muong ethnic groups are located on the Vietnamese border of Borikhamxay, in between the two Mon-Khmer settlements in the North and South. They represent the extension of the Vietnamese province of Nghe Tinh, where they form a sizeable majority (85% of the population). The Hor, belonging to the Sino-Tibetan family, are concentrated along the Chinese border in Phongsaly province.