An informal survey shows there are 38,000 fundamentalist Mormons in the U.S., Canada and Mexico -- up by 1,000.

"It is a conservative figure but that's the approximate figure for now," said Anne Wilde, a co-founder of the advocacy group Principle Voices, which conducts the periodic survey. Estimates for organized groups are provided by group leaders or council members. The count includes children and adults, living in both monogamous and polygamous families. Wilde said about half are in plural families.

"It's been kind of generally increasing but not in thousands, maybe in 50s or 100s," Wilde said. "There is the birth rate, there is some conversion rate in some of the groups, there is the death rate and some people leave. You've got to consider all that and take it into account but you are increasing in numbers."

Wilde released the survey Friday at a legal conference sponsored by Principle Voices, a nonprofit organization.

Surveys conducted by Wilde in 2005 and 2007 counted 37,000 fundamentalist Mormons.

Many fundamentalist Mormons -- 15,000 -- claim no affiliation with any group and are listed as Independents. Wilde's count of Independents is based on personal contacts and familiarity with family groups.

The largest group, now pegged at 10,000 members, is the Fundamentalist Church of Jesus Christ of Latter Day Saints. The FLDS are based in Utah, Arizona and Texas, but also have members in numerous other states, as well as Canada.

Wilde's count for the FLDS has fluctuated through the years. But for the first time this year, she was able to get an estimate directly from the FLDS.

"They confirmed 10,000," she said.

The second largest group is the Apostolic United Brethren, which has members living in Utah and Montana. It has 7,500 members, a count that has not changed since 2005.

Wilde also reports 2,000 members each for Centennial Park, based in northern Arizona, and the Davis County Cooperative Society, located primarily in the Salt Lake Valley.

brooke@sltrib.com