A new Barna research found that while a majority of Christians in America identify as Christians, only a minority are "practicing Christians" who attend the church at least once a month.

As many as 73 percent of the Americans say they are Christians, 20 percent identify as atheists or agnostics, 6 percent adhere to other faiths such as Islam, Buddhism, Judaism, Hinduism, and 1 percent are not sure.

The research found that those Americans who identify as Christians (73 percent) also say that faith was crucial in their lives.

However, when they are asked about how regularly they attended church, a much smaller proportion said they visited church often.

Only about 31 percent of the Americans said they attended church at least once a month, which is a criteria used by Barna group to classify people as "practicing Christians."

The study also put about 48 percent of the Americans under the category of "post-Christians." The post-Christians are those people who do not get engaged in activities such as Bible reading, prayer, and church attendance, and have disbelief in God or identify as atheists or agnostics. Individuals were termed as "post-Christian" when at least 60 percent of their responses were positive on the scale testing lack of involvement in church practices and feelings of disbelief.

Even though America has several big megachurches, the highest proportion of Christians (46 percent) attend churches with 100 or fewer members, about 37 percent go to a mid-sized church with 100-499 members, 9 percent attend churches with a member count ranging between 500 and 999, and only 8 percent went to large churches with over 1,000 attendees.

The study also found that Christians are more generous than secular Americans. As many as 96 percent of the practicing Christians donated to churches and nonprofits, but only 60 percent of the atheists and agnostics did so. An absolute majority (94 percent) of the practicing Christians donated to churches.

Overall, about 54 percent of the Americans donated to churches during the past year, and 22 percent gave money to nonprofits. The rest (24 percent) did not donate to any church or non-profit organization.

A majority of Americans (75 percent) said they prayed to God over the last week, and about 35 percent went to church in the last seven days. A significant minority of Americans (34 percent) claim to have read the Bible in their spare time at home over the last week.

Fewer American adults said that last week they volunteered at a non-profit (19 percent) or a church (18 percent). About the same proportion had attended Sunday school (17 percent) or a small group (16 percent).

The key faith groups identified by Barna are "born-again Christians," who have made a personal commitment to Jesus Christ and believe that they will go to heaven when they die; "Bible-minded Christians," who believe in the inerrancy of Bible; and "evangelical Christians" who are born-again as well as feel responsible to share their faith, believe that Satan exists, believe in Jesus Christ's sinless life on earth and salvation among other doctrinal views.

About 35 percent of the Americans were born-again Christians, 23 percent were Bible-minded, and some 7 percent professed evangelical faith.

The purpose of the study was to gauge the "state of the church" in America, the research group said, and was conducted during the first half of 2016. Over 5,000 adults were interviewed via internet and telephone across the US.