Protestant Christians now constitute the largest religious group in Korea thanks to the massive spread of evangelical or born-again churches, according to the latest government statistics.
Statistics Korea compiles data on the religious composition of the nation every 10 years, and the latest figures shows that 43.9 percent of Koreans practice some type of religion while the rest say they are non-believers. This is the first time more than half of the country are non-believers.
Protestant Christians, including non-evangelicals like Anglicans, accounted for 19.7 percent of the believers with 9.67 million people, Buddhists for 15.5 percent or 7.61 million, and Catholics for 7.9 percent or 3.89 million. Protestants have now overtaken Buddhists, who used to be the biggest group.
The proportion of non-believers is high among younger Koreans at 64.9 percent of those in their 20s and 62 percent among teens. But among people in their 60s, 57.7 percent said they practice a religion, rising to 58.2 percent among the over-70s.
The findings have upset some critics, who believe the methodology must be flawed if the decline in established religions is so steep. Unlike previous statistics, the latest data are based on a sample survey involving only 20 percent of the country's total households.
The sample group consisted of 10 million people, with 51.4 percent of the data gathered from door-to-door visits and 48.6 percent through Internet surveys.
A spokesperson for the Joggye Order of Buddhism said, "Many of our followers are senior citizens and that puts us at a disadvantage in terms of electronic survey methods."
And a Catholic spokesman said, "We conduct a detailed annual study on the number of followers and the latest figure was 5.65 million as of the end of 2015" as against the government tally of 3.89 million. "Even if borderline Catholics are considered, the difference between the figures is too high."
Cho Sung-don of the Graduate School of Practical Theology said, "It seems that the method had a huge impact on the results. Evangelical Christians are usually more politicized than followers of other religions and more active in taking part in the survey."
Statistics Korea defended the findings. "Samples of 20,000 to 30,000 people are used to compile national data, but the latest study involved 10 million people and the data can be viewed as accurate, and there were no problems from a statistical standpoint," a spokesman said.