> According to a Gallup International survey of more than 50,000 people in 57 countries, the number of individuals claiming to be religious fell from 77% to 68% between 2005 and 2011, while those who self-identified as atheist rose by 3% – bringing the world’s estimated proportion of adamant non-believers to 13%.<p>The World Religion Database disagrees, saying that the percentage of the world's population that is religious increased from 87.1% in 2000 to 88.2% in 2010. They suggest that growth is continuing due to the spread of Islam in Africa and Christianity in China: <a href="https://web.archive.org/web/20131020100448/http://media.johnwiley.com.au/product_data/excerpt/47/04706745/0470674547-196.pdf" rel="nofollow">https://web.archive.org/web/20131020100448/http://media.john...</a>