I think when it comes to surveying atheists there are some built in problems that makes assessment difficult. A lot of non believers do not identify with terms such as atheist, agnostic, nonreligious and non-theist which add to confusion among poll data.
Non belivers are now the 3rd largest group in religious-none religious surveys however the Atheist may only make up 3 or 4% of that.
It's also interesting to note:
a Canadian poll released September 12, 2011 sampled 1,129 Canadian adults and came up with some interesting unrelated data on the numbers of declared atheists...................... [ 6 ] . A quote from the study:
The data also revealed some interesting facts about Canadians beliefs:
- A majority (53%) of Canadians believe in God. What is of particular interest is that 28% of Protestants, 33% of Catholics, and 23% of those who attend weekly religious services do not.
- One quarter (23%) of those with no religious identity still believe in God." [ 7 ]
So if the retention rate is low there may be confusion in how some identify themselves, for instance would those that don't believe in god but still identify with the church they attend weekly call themselves atheists or Protestants or Catholics? When push comes to shove people join a church or organization for a variety of reasons none of which may be related to a belief in god.