Koreans are believed to be descendents of Altaic- or proto- Altaic-speaking tribes, linking them with Mongolians, Tungusics and Turkics. Archaeological evidence suggest proto-Koreans were Altaic-language-speaking migrants from south-central Siberia, who populated ancient Korea in successive waves from the Neolithic age to the Bronze Age.
Recent advances in the study of polymorphisms in the human Y-chromosome have produced evidence to suggest that the Korean people have a very long history as a distinct, mostly endogamous ethnic group, as male Koreans display a high frequency of Y-chromosomes belonging to Haplogroup O2b that are more or less specific to Korean populations.
Most Koreans and part-Koreans still display phenotypes suggesting Altaic origins. These features include higher cheekbones, and the Mongolian spot, a genetic predisposition for a bluish birthmark on the lower body which remains until early childhood; however, the Mongolian spot is also extremely common among non-Altaic people of Chinese, African, Native American, or East Indian ancestry.
Within South Korea, the most important regional difference is between the Gyeongsang region, embracing Gyeongsangbuk-do and Gyeongsangnam-do provinces in the southeast, and the Jeolla region, embracing Jeollabuk-do and Jeollanam-do provinces in the southwest. The two regions, separated by the Jiri Massif, nurture a rivalry said to reach back to the Three Kingdoms Period, which lasted from the fourth century to the seventh century A.D., when the kingdoms of Goguryeo, Baekje and Silla struggled for control of the peninsula.
Observers noted that interregional marriages are rare, and that as of 1990 a new fourlane highway completed in 1984 between Gwangju and Daegu, the capitals of Jeollanam-do and Gyeongsangbuk-do, completed in 1984, was unsuccessful in promoting travel between the two areas.
South Korea's political elite, including presidents Park Chung-hee, Chun Doo-hwan, and Roh Tae-woo, have come largely from the Gyeongsang region. As a result, Gyeongsang has been a special beneficiary of government development assistance.
By contrast, historically the Jeolla region has remained comparatively rural, undeveloped, and poor. Regional social disturbances intensified in the May 1980 Gwangju massacre, in which about 200 and perhaps many more inhabitants of the capital of Jeollanam-do were killed by Chun Doo-hwan's troops who were sent to quell demonstrations of citizens and students against military coup regime. The demonstration against military regime occurred all over the country, but only Gwangju was heavily damaged. Many of the troops who put down the demonstrations were reportedly from the rival Gyeongsang region.
Regional stereotypes, like regional dialects, have been breaking down under the influence of centralized education, nationwide media, and the several decades of population movement since the Korean War. Stereotypes remain important, however, in the eyes of many South Koreans. For example, the people of Gyeonggi-do, surrounding Seoul, are often described as being cultured, and Chungcheong people, inhabiting the region embracing Chungcheongbuk-do and Chungcheongnam-do provinces, are thought to be mild-mannered, manifesting true yangban virtues. The people of Gangwon-do in the northeast were viewed as poor and stolid, while Koreans from the northern provinces of Pyongan, Hwanghae, and Hamgyong, now in North Korea, are perceived as being diligent and aggressive. Jeju-do is known for its strong-minded and independent women.
Estimating the size, growth rate, sex ratio, and age structure of North Korea's population has been extremely difficult. Until release of official data in 1989, the 1963 edition of the North Korea Central Yearbook was the last official publication to disclose population figures. After 1963 demographers used varying methods to estimate the population. They either totaled the number of delegates elected to the Supreme People's Assembly (each delegate representing 50,000 people before 1962 and 30,000 people afterward) or relied on official statements that a certain number of persons, or percentage of the population, was engaged in a particular activity. Thus, on the basis of remarks made by President Kim Il Sung in 1977 concerning school attendance, the population that year was calculated at 17.2 million persons. During the 1980s, health statistics, including life expectancy and causes of mortality, were gradually made available to the outside world.
In 1989 the Central Statistics Bureau released demographic data to the United Nations Fund for Population Activities (UNFPA) in order to secure the UNFPA's assistance in holding North Korea's first nationwide census since the establishment of the state in 1948. Although the figures given to the United Nations might have been distorted, it appears that in line with other attempts to open itself to the outside world, the North Korean regime has also opened somewhat in the demographic realm. Although the country lacks trained demographers, accurate data on household registration, migration, and births and deaths are available to North Korean authorities. According to the United States scholar Nicholas Eberstadt and demographer Judith Banister, vital statistics and personal information on residents are kept by agencies on the ri (“village”, the local administrative unit) level in rural areas and the dong (“district” or “block”) level in urban areas.
Large-scale emigration from Korea began as early as the mid-1860s, mainly into the Russian Far East and Northeast China; these emigrants became the ancestors of the 2 million ethnic Koreans in China and several hundred thousand ethnic Koreans in Central Asia. During the Japanese colonial period of 1910-1945, Koreans were often recruited and or forced into labour service to work in mainland Japan, Karafuto Prefecture, and Manchukuo; the ones who chose to remain in Japan at the end of the war became known as Zainichi Koreans, while the roughly 40 thousand who were trapped in Karafuto after the Soviet invasion are typically referred to as Sakhalin Koreans. Korean emigration to America was known to have begun as early as 1903, but the Korean American community did not grow to a significant size until after the passage of the Immigration Reform Act of 1965; as of 2007, roughly 2 million Koreans emigrants and people of Korean descent live in the United States.
Large Koreatowns can also be found in Australia, Brazil, and Canada. The largest Korean community outside of Korea is in Los Angeles, California. Koreans in the United Kingdom now form Western Europe's largest Korean community; Koreans in Germany used to outnumber the ones in the UK until the late 1990s. There are also Koreatowns in Latin American countries such as Argentina, Guatemala, and Mexico. During the 1990s and 2000s, the number of Koreans in the Philippines and Koreans in Vietnam have also grown significantly.
The Korean population in the United States is a small share of the US economy, but it has a disproportionately favorable impact. The Koreans in the United States have a saving rate double that of the average American. Koreans in the United States graduate from college at a rate double that of the average American providing a highly skilled and educated addition to the US workforce. The second generation of Koreans has an average income 70% above that of the average American, indicating both their attainment and the contribution they make to the US economy. Marcus Noland, an expert on South Korea, the Korean economy, North Korea, and outlook for Korean unification, has claimed that if somehow the Korean-American population were to double, the US would experience a growth rate of per capita income by 0.1 to 0.2 percent.