Why is atheism so prevalent at western countries?

[tonoy]

Well, I suppose the title says it all. I guess to be more specific, I should emphasize particularly on Western European society. However, it's not to say that countries at East such as Japan and China should be ignored, where East Asian religion blurs the line between faith and Western Atheism. I suppose the politically correct(if there is any) way to ask this question would be "why is atheism more so prevalent at developed countries?"

I don't think neither Intelligence nor Education are the prime factor. I have met many Atheist and I am pretty sure not all of them will be categorized as an "Einsteinian genius". To be honest, I can't seem to find a very clear answer except maybe that, people in poorer countries simply don't have the luxury to ponder over such unanswerable questions. What are your thoughts in this matter?

PS. I do not intend to stir up any controversy. I was rather curious to find out what others' intake would be on this matter here at BC. And quite frankly, I was getting tired of people whining about the Moni-Mahal.