Americans are becoming less religious, judging by such markers as church attendance, prayer and belief in God, and the trend is more pronounced among young adults, a poll released Tuesday shows.

The share of U.S. adults who say they believe in God, while still high compared with other advanced industrial countries, slipped to 89 percent in 2014 from 92 percent in 2007, according to the Pew Research Center's Religious Landscape Study.

The proportion of Americans who say they are "absolutely certain" God exists fell even more, to 63 percent in 2014 from 71 percent in 2007.