Laos developed its culture and customs as the inland crossroads of trade and migration in Southeast Asia over millennia. As of 2012 Laos has a population of roughly 6.4 million spread over 236,800 km2 (91,400 sq miles), yielding one of the lowest population densities in Asia. Yet the country of Laos has an official count of over forty-seven ethnicities divided into 149 sub-groups and 80 different languages. The Lao Loum have throughout the country's history comprised the ethnic and linguistic majority. In Southeast Asia, traditional Lao culture is considered one of the Indic cultures (along with Burma, Thailand and Cambodia). Laos is geographically isolated and mountainous, bounded by the Annamite Range in the east, forming a traditional political and cultural boundary with Vietnam (a more Chinese influenced Sinitic culture). Much of the western borders of Laos are formed by the Mekong River which provided the major means of inland trade despite limited navigability along the river's length. Prior to the 20th century Lao principalities and the Kingdom of Lan Xang extended to the Sipsong Panna (China), Sipsong Chau Tai (Vietnam), and Khorat Plateau (today the northeast of Thailand) where the river was used as a transportation artery to connect Lao peoples on both the right and left banks. However, the political history of Laos has been complicated by frequent warfare and colonial conquests by European and regional rivals. The history of Laos is unique with a national character defined by its diversity in both culture and customs. Ethnicity Laos has an estimated population of 6.5 million. The Lao government recognizes 47 distinct ethnicities, which are further sub-divided into 149 subgroups. Lao society is traditionally categorized into three broad groups based on ethnicity and location. Approximately 50% of the total population is ethnic Lao (Lao Loum or Lao Tai); 10% are categorized as Lao Theung or “upland Lao” who are predominantly people of Mon or Khmer ancestry; another 34% are Lao Sung or “mountain Lao,” and are also commonly referred to as “hill tribes.” Hill peoples in Laos include the Hmong, Yao (Mien), Akha, and Lahu. Laos is also home to sizeable communities of Vietnamese and Chinese who make up the 6% remaining. Anthropologists consider the Lao Loum as a subcategory of the wider “Tai” ethnic group who share common genetic, linguistic, and cultural heritage. The Tai family includes the Lao and Thai, as well as smaller groups which have generally