A recent Pew study shows that non-belief is growing among Americans. Freelance researcher Gregory S. Paul has proposed a mechanism for this growth of non-belief. For instance, in 2009, he published on this topic in Evolutionary Psychology. More recently, in the February, 2010 edition of Science (available online only to subscribers), Paul gives a succinct summary of this proposed mechanism to explain declining popularity of religion in prosperous countries:

In modern nations, non-religion and the acceptance of evolution become popular when the middle-class majority feels sufficiently secure and safe, thanks to low income inequality, universal health care, job and retirement security, and lower rates of legal crime; this has occurred to greater and lesser degrees in most first-world countries, from Japan to Scandinavia. Religion thrives when the majority seek the aid and protection of supernatural powers because they are impoverished, is in third- and second-world countries or, in the case of the United States (the most religious and creationist first-world country), because a majority of Americans fear losing their middle-class status as a result of limited government support, high levels of social pathology, and intense economic come petition and income disparity. Prosperous modernity is proving to be the nemesis of religion.