China's Protestant community, which had just one million members in 1949, has already overtaken those of countries more commonly associated with an evangelical boom. In 2010 there were more than 58 million Protestants in China compared to 40 million in Brazil and 36 million in South Africa, according to the Pew Research Centre's Forum on Religion and Public Life.
Prof Yang, a leading expert on religion in China, believes that number will swell to around 160 million by 2025. That would likely put China ahead even of the United States, which had around 159 million Protestants in 2010 but whose congregations are in decline.
By 2030, China's total Christian population, including Catholics, would exceed 247 million, placing it above Mexico, Brazil and the United States as the largest Christian congregation in the world, he predicted.
"Mao thought he could eliminate religion. He thought he had accomplished this," Prof Yang said. "It's ironic – they didn't. They actually failed completely."