recruit Taiwanese chip industry talent to support its mandates resulted in the loss of more than 3,000 chip engineers to mainland China, and raised concerns of a "brain drain" in Taiwan. Many Taiwanese students attend cram schools, or buxiban, to improve skills and knowledge on problem solving against exams of subjects like mathematics, nature science, history and many others. Courses are available for most popular subjects and include lectures, reviews, private tutorial sessions, and recitations. , the literacy rate in Taiwan was 99.03 percent. Demographics Taiwan has a population of about 23.4 million, most of whom are on the island of Taiwan. The remainder live on the outlying islands of Penghu (101,758), Kinmen (127,723), and Matsu (12,506). Largest cities and counties The figures below are the March 2019 estimates for the twenty most populous administrative divisions; a different ranking exists when considering the total metropolitan area populations (in such rankings the Taipei-Keelung metro area is by far the largest agglomeration). The figures reflect the number of household registrations in each city, which may differ from the number of actual residents. Ethnic groups The ROC government reports that 95 per cent of the population is Han. There are also 2.4 per cent indigenous Austronesian peoples and 2.6 per cent new immigrants primarily from China and Southeast Asia. The overwhelming majority of Han are descendants of Hoklo and Hakka who arrived in large numbers in the 17th to 18th century. A minority are waishengren, descendants of Chinese nationalists who fled to Taiwan at the end of the Chinese Civil War in 1949. The Hoklo people, whose ancestors migrated from the coastal southern Fujian region, compose approximately 70 per cent of Taiwan's population. The Hakka comprise about 15 per cent of the total population, and descend from Han migrants from eastern Guangdong. Genetic studies also indicate that the Hoklo and Hakka people that make up majority of the Taiwanese population, are a mixture between Austronesians and Han people. The indigenous Taiwanese aborigines number about 584,000, and the government recognises 16 groups. The Ami, Atayal, Bunun, Kanakanavu, Kavalan, Paiwan, Puyuma, Rukai, Saisiyat, Saaroa, Sakizaya, Sediq, Thao, Truku and Tsou live mostly in the eastern half of the island, while the Yami inhabit Orchid Island. Languages Mandarin is the primary language used in business and education, and is spoken by the vast majority of the population. Traditional Chinese is used as the writing system. The