PROVO — Counting people is an inexact science.

Take Provo, for example.

A year ago, the U.S. Census Bureau estimated Provo was losing residents. The estimate dropped the city from its 2000 census of 105,116 to 99,624 people.

In October, it revised its estimate to 111,718. Provo said it should be 115,112.

Provo officials say a new estimate released this month is also incorrect. They and four other Utah County cities have challenged the census estimate numbers.

"It's the issue of getting a reliable count and letting them know that it's still wrong," said Raylene Ireland, Provo spokeswoman. "It's important especially since they regularly miscount us because of our student population, which seems to cause problems with the census. We feel it's important to stay on this until we know they have something that's accurate."

Provo's challenge is still pending. The newly released revised estimate for 2005 puts the city's population at 113,459, but Mountainland Association of Governments transportation planner Shawn Eliot believes the number should be more like 115,000.

And Provo isn't the only one with yo-yo population reports. Besides Provo, Mountainland Association of Governments has helped file challenges for the population estimates of American Fork, Salem, Mapleton and Elk Ridge.

American Fork preliminarily succeeded in getting its 2005 estimate raised to 25,131 from 21,372. Salem went up to 5,519 from 4,725; Mapleton is now 7,001, up from 5,972; and Elk Ridge's estimate is 2,251, up from 1,926.

Robert Spendlove, manager of demographic and economic analysis for the Governor's Office of Planning and Budget, said the cities' revised estimates have not yet been formally confirmed, but he knows many of them are working on challenges.

"This process is a fluid process," Spendlove said. "After census bureau estimates come out, there's a flood of activity. That's where we are now."

Most cities in Utah County have filed challenges at some point since the 2000 Census.

Eliot said the Mountainland Association of Governments has helped cities work on the challenges since May. The process was sped up this year after they received a heads up early on by the Census Bureau that some of the numbers might not look right.

"The census already knew the numbers were wrong in some areas," he said.

It's not that the U.S. Census Bureau is picking on Utah County, Eliot said. It's just that the demographics are unusual.

"Counties that have large student populations — they have a harder time tracking their growth," Eliot said. "There is a flaw in their methodology when it comes to these areas. The only way they feel we can get around it is by challenging."