Citing statistics for your purpose is a way around this, but the data isn't unambiguously in favor of atheism: there are a lot of confounding factors (income and education are the big ones), and some important metrics like self-identified happiness actually come out in favor of theism. That debate usually degenerates into a brawl over Puddleglum's Wager.

My understanding is that the statistics on this rate practicing religious adherents against people who are not practicing religious adherents. Although it could be that theism simply makes people happier on average, my primary hypothesis is that the social activity of church participation accounts for a lot of this. I've known priests who were amazing public speakers and community organizers, and I consider it a shame that strictly secular societies rarely provide proper venues for such people to put their skills to good effect.