So, it would appear that from 2004 to 2005, even your own information indicates the percentage of people who admit to being absolute atheists decreased and -- wow, by about 44 percent!!!!!!!
A 2008 poll by the Pew forum on religion and public life as summarized at
http://www.nj.com/news/index.ssf/200...elieve_ot.html
is more recent stating the number who believe in God or some sort of universal spirit was at 92 percent which I erroneously inflated to 93 percent. I note this study is four years more recent that the 2004 BBC poll you cite.
Even more shocking in that poll of 35,000 people is that only 1.6 percent of people in the U.S. considered themselves athists. A full copy of this poll can be found at
http://religions.pewforum.org/reports
It would seem to me, contrary to your contention, that the number of people who are dyed in the wool, out and out atheists is the group which is dramatically decreasing.