The U.S. is still home to more Christians than any other country in the world, and a large majority of the country identify with that faith. But the percentage of adults who call themselves Christian fell to 71% in 2014, down from 78% in 2007. Over the same period, the percentage of Americans who identify as atheist, agnostic or say they are “nothing in particular” climbed to 23% from 16%, the survey found.