Atheism is on the rise world wide, this we know. The details, of course, are trickier than that. Recently there was a large worldwide poll to discover trends in religious belief and the change over just a few years was really substantial. The same study was done in 2005 with a slightly different set of nations so comparisons can be done but they need to be done carefully. The question asked was
"Irrespective of whether you attend a place of worship or not, would you say you are a religious person, not a religious person or a convinced atheist?"
Worldwide the number of people answering 'religious' was 59%, non-religious was 23%, and confirmed atheist 13%. The survey revealed a number of trends within the data, most of which are unsurprising. Atheists tend to be young, educated, middle class or higher, and female. The male / female split is 12%/14% so the difference between the genders isn't huge but it is relatively easily explained by the very substantial sexism embedded in most of the largest religions. It is difficult to chart exactly how answers to these questions have changed though because of China. It was added to the 2012 survey but was not in the 2005 survey and China is both immense in population and the most atheist country in the world at 47%.
The thing that has me wondering is how much of this change towards atheism is people actually changing their minds on God and how much of it is people feeling that it is socially acceptable to identify as atheist? In Canada we have 46% religious, 40% not religious, 9% atheist, 5% unsure. That is an awful lot of people who believe that religion is not for them but that there is some kind of God. Since 2005 the number of religious folk has dropped from 58% to 46% but I find it hard to believe that so many people have actually changed their minds that quickly; most of that must be a change only in their answers. Some of them are surely people who were raised in a religious setting and completely ignore religion but who haven't really critically thought about their belief in God. Particularly when the question is phrased as "convinced atheist" there is a huge amount of room for uncertainty. It feels to me like we won't actually know what people believe until there is more time for atheism to set in as a normal, unremarkable option. Heck, there are still a few religious folk who confuse atheism with devil worship and that sort of nonsense is going to mess with your response accuracy.
It used to be that the default assumption was that you were a Christian who went to church. That slowly eroded to the current situation where the default assumption is that you are a cultural Christian who doesn't go to church but has some residual beliefs from a religious upbringing. (I still remember getting Christian education in public school from the nice old lady who came to tell us Bible stories every couple weeks. Unsurprisingly she left out the mass murders, rapes, torture, slavery, genocides, and other such atrocities.) The trend is definitely shifting towards an assumption of agnosticism for some, atheism for others, but what that trend looks like is really hard to know.
There is an amusing article on this on the bbc website. They have a couple opinion pieces after the actual facts from two very different viewpoints. The right wing Christian viewpoint seems to be that progression churches are ruining it for everybody by watering down religion and supporting the people who 'believe in God' but who ignore religion. Apparently people without religion don't have the strength to deal with a hard life and when they come crawling back to Christianity only the serious churches that maintained their hard line on bigotry will be left. The left wing opinion is that churches that continue to pursue homophobic and sexist policies are doomed because young people won't put up with that these days. Only those churches that are willing to be progressive and inclusive have any chance. I doubt that either have any chance at all to remain large scale and influential in the long term; the important point is that they need to do the right thing now.