The classification of ethnic groups in Indonesia is not rigid and in some cases unclear due to migrations, cultural and linguistic influences; for example some may consider Bantenese and Cirebonese to be members of Javanese people, however some others argue that they are different ethnic groups altogether since they have their own distinct dialects. This is the same case with Baduy people that share many cultural similarities with the Sundanese people. An example of hybrid ethnicity is the Betawi people, descended not only from marriages between different peoples in Indonesia but also with Arab and Chinese migrants since the era of colonial Batavia (Jakarta).
The proportions of Indonesian ethnic groups according to the (2000 census) are as follows:
The regions of Indonesia have some of their indigenous ethnic groups. Due to migration within Indonesia (as part of government transmigration programs or otherwise), there are significant populations of ethic groups who reside outside of their traditional regions.
Arabs: Historically Arab traders were credited for the spread of Islam in the Indonesian archipelago. Many have assimilated into local ethnicities such as Betawi, Malay, Javanese, and Sundanese; however, several cities in Indonesia have significant Arab populations that preserve their culture, identity, and their links to Arabic countries. Spread throughout Indonesian cities, significant numbers can be found in Surabaya, Gresik, Jakarta, Medan and many coastal cities in Indonesia.
Indian: Indian people also had settled the Indonesian archipelago, however their number is not as large as that of Chinese Indonesians. Concentrated in urban centers with significant numbers around Pasar Baru in Jakarta, and Kampung Keling in Medan.
Indos: Indos or Eurasians, of mixed ancestry between Indonesian native ethnic groups and European/Dutch ancestry, they emerged during the Dutch East Indies period. Around one million Indonesians with various degrees of mixed ancestry today can trace their ancestry to Europeans. During the colonial period, their numbers were greater, but since Indonesian independence most chose to go to the Netherlands. Eurasian Indonesians dwindle in number as an ethnic group since major emigration from Indonesia after World War II.
Japanese: Japanese have migrated to Indonesia since the Dutch East Indies colonial era; however, after their defeat in World War II, their number decreased, leaving small numbers of ex-Japanese soldiers that still stayed in Indonesia and became Indonesian citizens. The recent development of Japanese residents in Indonesia was driven by the increase of Japanese business and investment in Indonesia since the 1970s, and mostly are expatriates that still maintain their Japanese citizenship. Significant numbers of Japanese expatriates stay in Indonesia, especially in Jakarta and Bali.
Korean: They are a recent addition of Indonesian foreign origin ethnicities, dated back only several decades ago. Mostly driven by the increase of Korean business and investment in Indonesia, and most are expatriates that still maintain their Korean citizenship.