"According to the 2001 American Religious Identification Survey conducted by the U.S. Census, 15 percent of the adult population is atheistic, agnostic or otherwise non-religious. In comparison, Jews and Mormons each constitute 1.4 percent of the population, 0.6 percent of Americans are Muslims, and 0.05 percent are Buddhists.(But of course Atheism is not a belief. ;) )
Yet in the U.S. Congress and Senate, the religious demographics do not match up with those of the population. Among the 535 members, only one representative - Pete Stark, D-Calif. - is publicly non-religious. This comes to roughly 0.2 percent of the whole membership of Congress, compared to 15 percent of the public."
Linsen Li, The Kentucky Kernel, Apr 2, 2007