Higgins Strategy

Buddhism Across Asia

How Buddhism spread from the Ganges plain to Japan, about 251 BCE to 552 CE, and why it alone of Pew’s seven groups shrank from 2010 to 2020.

Britannica dates the Buddha to c. 6th–4th century BCE. In 2020 there were 324 million Buddhists, 4.1% of the world, by the Pew Research Center’s estimate, down from 343 million in 2010. They were the only one of the seven groups Pew counts whose number fell.

The spread across Asia

Britannica describes the “vigorous patronage of Buddhism” of the Mauryan emperor Ashoka during his reign, c. 265–238 BCE (also given as c. 273–232 BCE). It dates the mission of his son Mahendra to Sri Lanka to about 251 BCE; says Buddhism “is thought to have been introduced” to China during the reign of the emperor Mingdi, 57–75 CE; and dates its introduction to the Korean kingdom of Goguryeo to 372 CE and to Japan, by two traditions, to 538 or 552. The monument at Borobudur on Java was built about 778–850 CE. In India the monastery at Nalanda was sacked c. 1200 and, in Britannica’s words, “never recovered” (Exhibit 27).

27. Buddhism reached Sri Lanka about 251 BCE, China under the emperor Mingdi (57–75 CE), Korea in 372 and Japan in 538 or 552

Source. “Buddha”; “Ashoka”; “Nalanda”; “Mahendra”; “Mingdi”; “Goguryeo”; “Japan: Yamato decline and the introduction of Buddhism”; “Borobudur”; “The Diamond Sutra” (International Dunhuang Programme)

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Method. Magadha stands for three sites in Bihar: Bodh Gaya, Pataliputra and Nalanda. Arrows are schematic and do not trace routes; Dunhuang marks where the 868 Diamond Sutra was found.

A woodblock-printed scroll: a frontispiece of the Buddha preaching, then columns of Chinese text
The Diamond Sutra, printed in 868 and found at Dunhuang; the British Library calls it the world’s earliest dated printed book (Or.8210/P.2). Image: British Library, Or. 8210/P.2. No known copyright restrictions.

The decline from 2010 to 2020

Most of the decline came from two countries. Pew counts 22.7 million fewer Buddhists in China in 2020 than in 2010 and 6.6 million fewer in Japan; South Korea lost 2.6 million. Thailand, with 67.6 million, had the most Buddhists in 2020, and Myanmar, Cambodia and Sri Lanka each gained (Exhibit 28). Buddhists were a majority in seven countries (Exhibit 29).

28. China lost 22.7 million Buddhists between 2010 and 2020 and Japan 6.6 million; Myanmar gained 4.25 million and Thailand 3.5 million

Source. Pew Research Center, Religious Composition by Country, 2010–2020, rounded counts.

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Method. Rounded counts as published; change is the 2020 count less the 2010 count.

Pew links the decline to two forces set out in the overview. Buddhists had the oldest median age of any group in 2020, 39.8 years. And more people leave Buddhism than join it: per 100 adults raised Buddhist, 22.1 have left and 12.3 have joined.

29. Buddhists were a majority in seven countries in 2020: Cambodia, Thailand, Myanmar, Bhutan, Sri Lanka, Laos and Mongolia

Source. Pew Research Center, Religious Composition by Country, 2010–2020, percentages. Country shapes: Natural Earth.

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Method. Outlined places have no estimate.

Two counts

How many Buddhists there are depends on who counts. The World Christian Database puts the number at 531 million in 2020, 207 million more than Pew, and counts a further 453 million Chinese folk-religionists (Exhibit 30). The difference is concentrated in China, where a third of adults say they believe in the Buddha or a bodhisattva and 4% say Buddhism is their religion, by the surveys Pew analyzed in 2023; the part on Taoism and Chinese religion charts those measures.

30. Gordon-Conwell counted 531 million Buddhists in 2020 and Pew 324 million

Source. Pew Research Center, Religious Composition by Country, 2010–2020; Gordon-Conwell, Status of Global Christianity, 2025 (World Christian Database), 1900–2050.

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Method. Gordon-Conwell counts Chinese folk-religionists as a separate group; Pew includes many of the same people among the unaffiliated or other religions.

Limitations (5)

  • Unverified. Counts of Theravada, Mahayana and Vajrayana Buddhists are not charted: no free primary source for a global split was found.
  • Conflicting sources. Ashoka’s reign: Britannica gives c. 265–238 BCE and also c. 273–232 BCE. Japan: Britannica gives 538 or 552 on one page and 552 on its Asuka period page.
  • Conflicting sources. Nalanda: Britannica dates the sack to about 1200; UNESCO refers to the sack and abandonment in the 13th century.
  • Conflicting sources. Pew (324 million) and Gordon-Conwell (531 million) differ on the number of Buddhists in 2020 (Exhibit 30).
  • Method. Arrows on Exhibit 27 are schematic; the sources give dates of introduction, not routes.

Sources (6)

  1. British Library: “The Diamond Sutra” (International Dunhuang Programme)
  2. Center for the Study of Global Christianity, Gordon-Conwell Theological Seminary: “Status of Global Christianity, 2025, in the Context of 1900–2050” (World Christian Database)
  3. Encyclopaedia Britannica: “Asuka period”; “Buddha”; “Ashoka”; “Nalanda”; “Mahendra”; “Mingdi”; “Goguryeo”; “Japan: Yamato decline and the introduction of Buddhism”; “Borobudur”
  4. Natural Earth: Admin 0 country boundaries, 1:110m and 1:50m (via world-atlas 2.0.2)
  5. Pew Research Center: “How the Global Religious Landscape Changed From 2010 to 2020,” June 9, 2025; Religious Composition by Country, 2010–2020, dataset and country table, 2025 (updated Feb. 12, 2026); “Measuring Religion in China,” Aug. 30, 2023
  6. UNESCO World Heritage Centre: “Archaeological Site of Nalanda Mahavihara”

Read next

The World’s Religions, part 4 of 7.

Next: Study XXVI, Taoism and Chinese Religion