Audacious Epigone has nice pie-charts worked out measuring belief in God across many groups. The usual suspects, he calls them, which is about right.
Nothing shocking, to my mind, though there were a few oddities I didn't have immediate theories for, such at the absence of atheists among Native Americans. Anyone who plays with these kinds of questions is aware that definitions are slippery, not so much because the questions aren't asked well, but because many people really don't think very clearly about such matters, including those he rates by wordsum as Really Smart. Many of those who describe themselves as "firm believers" and think of themselves as Christian may actually be congenitally truculent believers in some second-cousin to any traditional trinitarian faith. Alternatively, "uncertain believers" may be those who hedge their bets even when quite sure, and "agnostics" may include those who don't much care about the question either way, rather than those who have an opinion on the possibility of knowledge.
Now that the fun surveys have come out - much loved by preachers this year - that even some atheists pray, you can't even count on that as a clean category. Still, the breakdowns probably represent something real, and relatively close to the categories listed.
When these numbers are run and posted, there is sometimes an agenda behind that, such as attempting to show that a majority of even the smartest people believe, or its counterpunch, that fewer people are firm believers as one moves up the intelligence and educational scales. (I don't know if AE is trying to make some such point, BTW.) I would like to offer one complicating factor that I have never seen mentioned: that intelligent a/o educated people are more likely to question just about anything, including their current positions. In my experience there are intelligent atheists who question their own atheism at times, and agnostics who wonder if they are really just avoiding thinking hard. There are uncertain believers who wonder in both directions - whether their uncertainty is a halfway point to disbelief, to strong belief, or their natural dwelling. And, even those who eventually decide they have firm belief may have days when it all looks very doubtful.
Of all the results, the one that should concern believers is the breakdown by age. I think the gradual abandonment of firm belief and even uncertain belief in favor of atheism or agnosticism among the young is a real trend, and I don't see any factors that will reverse it. Popular preachers and contemporary Christian musicians to the contrary, I don't think believers acting like believers, darn it, will amaze the world and bring revival to this land. While some are drifting (or marching) away for some reasons that we might recognise as logical even if we disagreed with them, most young people are leaving because we are out of fashion. There have been ages when faith was in fashion (and thus consequently a mile wide and an inch deep), and it goes in and out of fashion among various groups. The next groundswell of fashion is likely underway and not visible to folks like me who aren't deeply embedded in modern culture. But for the time being, we will continue to be the Tyrolean hats of the belief world. (Unless those have recently come back? In which case, porkpie hats.)