The number of Christians in America who are actively practicing their faith has fallen by about half since 2000, according to a new survey.

A survey commissioned by the Barna Group indicates what the report calls a "dramatic change" in American Christianity. The Barna Group qualifies a "practicing Christian" by a respondent "calling oneself a Christian, strongly prioritizing faith and regular church attendance." By these measures, only 25 percent of respondents qualify as practicing, versus 45 percent in 2000.

The survey also showed a doubling in the number of American atheists and agnostics, and that an equal number of respondents became non-practicing Christians as those who left the faith completely.