Canada is one of many countries experiencing a significant decline in religiosity, according to a new report that found the number of people around the world who claim to be religious dropped 9% since 2005, while atheism rose 3%.

More than 51,000 men and women in 57 countries were asked, "Irrespective of whether you attend a place of worship or not, would you say you are a religious person, not a religious person or a convinced atheist?"

The Global Index of Religion and Atheism found 59% of respondents think of themselves as religious, 23% as not religious and 13% as convinced atheists.

China has the largest population of atheists (47%). Ghana has the largest population of people who consider themselves religious (96%). Meanwhile, Ireland, once above average in religiosity but rocked by numerous child sex abuse scandals involving the Catholic church, had a drop in those claiming to be religious - from 69% to 47%. Only Vietnam saw a bigger decline, from 53% to 30%. Canada is ninth on the list, with a 12% drop.

The study also found that religiosity declines when people prosper.

"People in bottom income groups are 17% more religious than those in the top income groups. The richer you get, the less religious you define yourself," according to the study.

The study was conducted by WIN-Gallup International between November 2011 and January 2012, with a margin of error of 3-5 percentage points at 95% confidence level.