Meanwhile, Herriman in southwestern Salt Lake County, which incorporated in 1999, is booming. Its population of about 1,500, according to the 2000 estimates base, has grown by more than 400 percent to an estimated 7,826 — an average growth rate of 50 percent per year.

Two northwestern Utah County cities that incorporated in the 1990s, Saratoga Springs and Eagle Mountain, are also among the state's fastest-growing cities.

With an addition of 4,846 people, West Jordan, with a total population estimated at 89,011, had the most overall population growth.

St. George, which grew by 3,256 people to an estimated 59,780, was second in growth, followed by Lehi, which gained 2,583 in one year — a growth rate of 11.2 percent to 25,665.

The Census Bureau's population estimates are used for distribution of road funds and sales tax for communities and are also tied to federal grants, Spendlove said.

Provo Mayor Billings expressed concern that if Provo's population is underestimated, it could force the city to raise taxes for residents.

"We have been closely watching the methods the Census Bureau uses because the Census Bureau (numbers) are coming in lower than where we think the cities should be and what the cities think they should be," Spendlove said.

Spendlove said four of the six Utah cities that produced evidence to successfully challenge their 2003 estimates — Genola, Highland, Pleasant Grove and Orem — are in Utah County.

Greg Harper, demographer for the U.S. Census Bureau, said all the places in a county have to add up to the county's population total. In most counties, the differences between the census' methods of estimation aren't as great as they are in Utah County, he said.

"In Utah County, a large number of places are challenging; that is unusual," Harper said.

Harper said some reasons for the differences could be changes in vacancy rates or population per housing unit, which the Census Bureau estimates using the 2000 Census.

While Provo is concerned about its estimate, Salt Lake City doesn't seem worried, nor does Ogden, which showed a 2004 population of about 78,500 — virtually unchanged from the previous year.

Ogden Mayor Matthew Godfrey said he wouldn't describe his city's growth as "stagnant."

Ogden has recently added about 350 downtown units, and he expects that to double or triple over the next few years, he said.

"We're introducing new housing to an urban center that hasn't had new housing, literally, in a hundred years," he said. "We've got good momentum here in downtown. It's a good place to live."

Neil Olsen, principal planner for Salt Lake City's Planning Division, said, "I don't think anyone here is wringing their hands."