How many Christians are there in China? It depends what you mean when you say "Christians". It depends if you're going to count recognized official congregations and/or the unofficial ones. And then there's the question of the houses churches which spring into existence constantly.
The BBC has an excellent essay on the whole situation which begins by pointing out that the Chinese government sees Roman Catholicism as a separate religion from "Protestantism".
"The government says 25 million, 18 million Protestants and six million Catholics. Independent estimates all agree this is a vast underestimate. A conservative figure is 60 million. There are already more Chinese at church on a Sunday than in the whole of Europe.
The new converts can be found from peasants in the remote rural villages to the sophisticated young middle class in the booming cities."
What's particularly interesting is the attempt by the author, Tim Gardam, to uncover the reason for this boom. According to the people he contacted, the Chinese decision to pursue capitalist growth, and "beautiful wealth" has created a spiritual vacuum in Chinese society.
"As one of China's most eminent philosophers of religion - Professor He Guanghu, at Renmin University in Beijing put it to me: "The worship of Mammon… has become many people's life purpose.
"I think it is very natural that many other people will not be satisfied... will seek some meaning for their lives so that when Christianity falls into their lives, they will seize it very tightly."
Sounds somewhat familiar, no?