WASHINGTON - The number of Americans who identify themselves as Christians has dropped nearly 8 percentage points in the last seven years, according to a new survey done by Pew Research Center.

The survey, entitled "Religious Landscape Study" and the Center's second of the kind, has found that 70.6 percent of Americans identified as Christians in 2014, down from 78.4 percent in 2007, according to a document about the survey which is available on the Center's website.

The survey also shows Americans identifying as having no religion grew from 16 percent to 23 percent, which means a population between 50 million to 73 million do not observe any religion.

At the same time, the research found that almost every major branch of the Christianity in the US has lost a significant number of members, mainly because young people are leaving the fold. More than one-third of young people now say they are unaffiliated with any religion, up 10 percent since 2007.

Pew researchers believed that the decline of Christian population was driven mainly by a falling trend of the country's most formidable faith traditions: Catholics and liberal Protestants, which occurred in all regions, among all ages and demographics of the US.

"We've known that the religiously unaffiliated has been growing for decades," said Greg Smith, a researcher of the new study. He nevertheless stressed the pace of growing "is really astounding."

Despite all of the latest developments, the United States remains home to more Christians than any other country in the world, claimed the survey, which was conducted between June 4 and Sept 30, 2014, among 35,071 adults via telephone interviews, with the margin of error of less 1 percentage point.