(RNS) June 7--Giving to churches and other nonprofit groups declined in 2000 and fewer people actually tithe than claim to follow the practice, Barna Research Group has found.

Seventy-eight percent of American adults donated money to a church or other nonprofit organization last year, a drop of 6 percentage points from the previous year and 9 points from 1998.

The average per-person giving to such charitable organizations decreased 15 percent in 2000 to a mean of $886. The mean was $1,045 in 1999 and $1,377 in 1998.

Researchers for the Ventura, Calif., research firm polled a random sample of 1,005 adults and asked them whether they tithe, how much they donated to houses of worship and the amount of their household income.

Although 17 percent of adults claimed to tithe, when researchers compared the amount they gave to their house of worship and their household income, they found that only 6 percent actually donated one-tenth of their income to that religious charity.

The 6 percent figure is based on the liberal definition of tithing because there is a debate over whether tithing should be based on pre-tax or post-tax income, said David Kinnaman, vice president of Barna Research Group.

Despite the decline in giving, churches remain the most likely groups to receive individual financial support. Sixty-one percent of adults donated money to one or more churches in 2000, compared to 66 percent in 1999. The average church donor contributed a mean of $649 to churches in 2000, compared to $806 in 1999.

George Barna, president of the research company, said churches may need to adjust as young adults "barely" give to religious causes and baby boomers--those in their mid-30s to mid-50s--do not always share their generosity with churches.

"They are value-donors, giving to organizations that they perceive to be providing personal benefits or significant, unduplicated value to society," Barna said in a statement. "As these two generations become more prolific within churches, their tendency to give less to churches will challenge ministries to reconceptualize their budgeting, fund-raising and planning practices."

The poll, based on telephone interviews, had a margin of error of plus or minus 3 percentage points.