The only study I’ve ever seen of atheists in jail is from 1997 and it shows that we make up only 0.2% of the U.S. prison population.
Some more recent statistics about prisoners were just released in England.
|Church of England||23,039|
Here’s how Martin Beckford of the Telegraph puts it:
Christians remain the best represented group behind bars, with 41,839 worshippers, while those declaring themselves to have no religion, or atheist or agnostic views, now stand at 27,710.
“No religion” includes people who don’t think about religion and who may have no stance about God whatsoever. It may also include religious people who don’t want to answer that particular question.
To assume “No religion” is synonymous with “non-theist” is incorrect.
Atheists (and even agnostics) do take a position on the nature of God — they have put some thought into it and attached a label to their way of thinking.
In any case, the 570 atheists in English prisons make up 1% of the population there.
That number is still far below the percentage of atheists in the general population, especially in the UK.
(Thanks to hoverfrog for the link!)