Shelly Andresen had thought her family was complete with three children, but now that it's bigger, she wouldn't have it any other way.

"We just enjoy them," she said of her six children, who range in age from 4 to 18 years. "It's not perfect all the time; we just do our best."

Utah has long had a higher fertility rate than the rest of the United States, though it is declining along with the nation's. In 1960, Utah had a fertility rate of 4.3 compared to the nation's 3.1. In 2004, Utah had a fertility rate of 2.5 compared to the nation's 2.0, said Pamela Perlich, senior research economist at the University of Utah's Bureau of Economic and Business Research.

Perlich said Utah has followed the national trend of decreasing fertility rates and smaller households since the baby boom following World War II. Part of that trend has to do with people living longer, so there are more retirees in households of one or two people, she said.

"It's a downward slope, but Utah is above the nation," she said. "It does not just have to do with the fertility rate; it also has to do with people living longer."

However, unlike the nation, Utah still has a fertility rate above replacement levels, and it experienced an acceleration in the 1980s.

"Right now we're in a pattern of constant fertility rate in Utah for the next little while," Perlich said.

For those with large families, faith often plays a role, said David Dollahite, professor of family life at Brigham Young University. Dollahite, who has seven children, said data has shown that those who are devout in their faith are more likely to have large families.

"Strongly held faith tends to lead toward larger families," he said. "The LDS influence on welcoming as many children as possible into the home certainly has an influence in Utah."

"It's not just a Utah Mormon thing, it's a religious thing," he said, noting devout Catholics, Orthodox Jews and the Amish are among those who also tend to have larger families.

"The data show a positive relationship between religiosity and fertility," he said.

The Church of Jesus Christ of Latter-day Saints has long considered traditional families to be the foundation of society but has stopped short of saying those families should be large.

"The (LDS) Church views the bearing and rearing of children by a married couple to be a joyful blessing," LDS Church spokesman Dale Bills said in a statement. "However, the decision as to how many children to have and when to have them is a private matter left between the couple and the Lord."