Between 2007 and 2014, the number of adults who self-identified as Christian fell from 78.4 percent to 70.6 percent, or 172.8 million people, driven mainly by drops among Roman Catholics and some Protestants, according to the Pew Research Center poll.
Non-religious U.S. adults who identify as atheist, agnostic or of no particular faith have seen their ranks swell over that same time period by about 6 percentage points to 22.8 percent of the population, or 56 million people.
Respondents who identified as Jewish rose 0.2 percentage points to nearly 2 percent of the population, while those identifying as Muslim more than doubled to 0.9 percent. Those who identified as Hindus rose slightly to 0.7 percent, and the number of Buddhists was unchanged at 0.7 percent.
The poll surveyed roughly 35,000 adults across the United States between June and September 2014 by telephone. The margin of error is plus or minus 0.6 percentage points.