I will agree that the actual number of “self-declared” atheists is open to interpretation and difficult to define. But there are likely 800 million to a billion atheists or agnostics in the world, even if they pass under other definitions.
This site implies that "The world population of non religious** ranges anywhere from 850 million to 1.1 billion making up 15 to 26.8%. The two ** refer to the fact that “** the ambiguous term non religious as used above includes those identified as atheist, agnostic, secular, nonbeliever and non-religious as defined by those responsible for the polls and statistics.”
In my opinion, the constant bad-mouthing and negativity directed towards atheism/agnosticism in most societies leads to a great many “disguised” atheists and agnostics.
It is a bit like all the women in our society who in making justified demands for gender equality preface their remarks with "I’m no feminist, but. . . . " Whenever I hear a woman say this, I begin asking them what they think on a series of gender-equality issues. Then I usually say, “Guess what, sweetie, you’re a feminist!”
The reason they refuse to self-identify as feminists is that they have been given a negative stereotype of fanatical, obnoxious, man-hating, ball-busting, nose-hair braiding, sweaty, masculine creatures with unshaven legs who are “probably dykes”.
I suspect a lot of virtual atheists and agnostics refuse to self-identify as such because of similar negative stereotypes.
For example, note the HUGE difference between the US figures for atheists, agnostics and “non-religious/secular” Americans in these self-identification figures for 2001:
Nonreligious/Secular 13.2% 27,539,000
Atheist 0.4% 902,000
Agnostic 0.5% 991,000
I cannot believe there are not several million “godless” Americans hiding in that 27 million!
In other cases, it is simply that a census or a survey has no time to deal with fine shades of meaning. You are a Baptist or Catholic or not. But the “non-religious” are almost by definition free-thinkers who resist labels and are difficult to classify.
For example, my own country, Canada, has a census category called “no religion” that groups all atheists, agnostics, and everyone else, including people who in my opinion are agnostics or atheists but will not admit it in so many words. The “no-religion” category has grown by 48% since the last census, and now represents over 16% of the Canadian population.
People who no longer practice any religion they were raised in, and are part of no organized church but who say they believe in the “power of love in the world” or some such generality will often reject being labeled agnostics or atheists, and the census has no time or capacity to dig deeper to see what they really are.
Given that there must at least be several hundred million atheists and agnostics in the world, it is still surprising that this report deals with NOT A SINGLE CASE.
Of course, this IS a Commission of the government of a country where they see nothing wrong in declaring that God exists on several billion currency notes. A country where “Condi” Rice often leads the Cabinet in prayer. A government that favours giving public money to religions’ “faith based” charities.
It would probably not be politically wise to show too much concern for atheists.