The main island was inhabited by a diversity of Taiwanese indigenous peoples speaking Austronesian languages until Han settlement began in the early 17th century, around the time of the Ming–Qing transition, when workers were mainly imported from Minnan region to the colony of Dutch Formosa in the southwest of Taiwan.

According to governmental statistics, in the early 21st century, 95% to 97% of Taiwan's population are Han Chinese, while about 2.3% are Taiwanese of Austronesian ethnicity.

[12] Demographic transition models (DTM) show how population pyramids change and go through specific stages.

Knowledge of and access to contraception, along with an increase in women's participation in the workforce, cause a sharp decline in the fertility rate.

For example, developing countries with limited access to healthcare and contraceptives, where populations have a high fertility rate, tend to have a lower proportion of older people.

[19] Medical advancements, industrial developments, and better knowledge of sanitation, which started in the 18th century in many developed countries, have caused a decline in mortality rates and an increase in fertility rates, factors which raise the number of older people worldwide.

[22] The CEPD estimated that the percentage of people 65 years or older will be over 20% in 2025, which means Taiwan will soon become a "super aged society".

[23] The critical factors that accelerate the speed of aging in Taiwan are high life expectancy and low fertility rate.

[24] According to a 2015 study by the Ministry of Health and Welfare, approximately 40% of Taiwan elders see themselves as a burden on family or society.

[30] Most women in developed countries are in the workforce and tend to have higher educations and professional careers.

[44] These groups primarily inhabit the eastern half of Taiwan, which consists mostly of mountainous terrain.

[47] In the early 1910s, research in the Japanese era recognized nine ethnic groups: Amis, Atayal, Bunun, Paiwan, Puyuma, Rukai, Saisiyat, Tsou, and Yami.

New ethnic groups were also recognized by the government, including Thao in 2001, Kavalan in 2002, Truku (Taroko) in 2004, Sakizaya in 2007, Seediq in 2008, Kanakanavu in 2014, and Saaroa in 2014.

The majority of Han Chinese descend from immigrants who arrived to the island prior to Japanese rule (1895–1945) and can be classified as the Hoklo and Hakka, on the basis of language and customs.

[50] As the majority of early immigrants were Hokkien speakers from Fujian[51] who arrived starting in the 17th century, the Hoklos account for about 70% of the total population today.

Almost everyone in Taiwan born after the early 1950s can speak Mandarin,[64] which was the official language and has been the medium of instruction in schools ever since.

Hanyu Pinyin, the official romanization system in mainland China, has also been the standard of Taiwan since 2009.

The majority speak Taiwanese Hokkien, a branch of Southern Min, which had formerly been the most commonly spoken language.

The other aboriginal languages that have gained official recognition are Kanakanavu, Kavalan, Puyuma, Rukai, Hla’alua, Saisiyat, Sakizaya, Seediq (closely related to Truku), Thao, Tsou, and Yami (also known as Tao).

As of 2013[update], the Republic of China government recognizes 27 religions which are registered with the Civil Affairs Department of the Ministry of the Interior (MOI).

Chinese folk religion is generally practised under the aegis of Taoism, while more than 10% of the population adheres to popular movements of salvation.

Christian churches have been active in Taiwan for centuries; a majority of them are Protestant, with Presbyterians playing a particularly significant role.

Islam has seen a surge in recent years as a result of foreign Muslims seeking work in Taiwan, most notably from Indonesia.

The table below shows official statistics on religion issued by the Department of Civil Affairs, Ministry of the Interior ("MOI"), in 2005.