WASILLA -- Growth in Mat-Su is slowing, according to state population estimates released earlier this year. And according to the state, more than a third of the borough's census-designated places lost a few residents.

Mat-Su Borough officials say the growth might be slowing, but it's nowhere near stopping. "We've had one heck of a run," said borough economic development director Dave Hanson. "And 2.6 (percent) is a very healthy growth rate."

Despite the slowing, Mat-Su continued to be the fastest-growing area in the state, a title the Valley has held since 1990.

The Valley population between 2000 and 2009 jumped from 59,322 to 84,314, an increase of 42 percent. The average rate of growth was about 3.8 percent each year during that time, according to the state.

Hanson pointed out that adding 25,000 residents to the borough has driven up demand for local services. The borough has a long list of roads that are overused and in need of repair, including three state-designated traffic safety corridors.

The slower rate of growth also doesn't diminish the need for new schools, said Mat-Su School District spokeswoman Catherine Esary. "We went from 12,699 students in 1999 to 16,673 this year. At its highest, we were seeing a 5.3 percent gain," she said.

The Mat-Su School District has opened nine new schools since 1999. That list includes Su-Valley Junior/Senior High School, built to replace a school that burned, but Esary said all other schools were built to decrease crowding.

Despite all that construction, she estimated between 1,800 and 2,000 students attend classes in portable classrooms. The district hasn't seen much of a slow-down in the growth of its student population, nor does it expect to.

District officials expect to continue seeing 1-percent to 2.5-percent growth rates, she said. With 3,500 soldiers scheduled to return to Elmendorf and Fort Richardson this spring, she said the district might see a small spike in its population.

Mat-Su has been living a culture of growth for a decade but not everywhere in the Valley is booming. Thirteen of 28 so-called census-designated places measured in Mat-Su lost population. Most lost just a few people, like Chase, the off-road community north of Talkeetna, which lost one of its 36 residents in 2009. But some of the losses came in unexpected places, such as Farm Loop and Lazy Mountain, both popular and fairly close-knit communities near Palmer. The state shows Farm Loop lost 33 people and Lazy Mountain nine.

One of the biggest puzzles is the loss of 53 people from Gateway, the community that straddles Trunk Road and the Parks Highway near its intersection with the Glenn Highway. It's close to the hospital, an easy spot for commuters to live and there are several nice recreation spots nearby.

"It really surprises me that there would be any loss," said Neil Fox, Gateway Community Council president. "This continues to be one of the most sought-after areas for recreation and for living."

Some of the loss might have come from houses purchased to make way for the Trunk Road project sweeping through the Gateway Community. State Transportation Department right-of-way agents bought 5 homes, which would have displaced about a dozen people.

State demographer Gregory Williams, who put together the new population figures, said he doesn't delve into the reasons numbers go up or down around the state.

Houston officials are also scratching their heads. The state says the Valley's smallest city, with an estimated population of 1,664, lost 64 residents between 2008 and 2009. Houston Mayor Roger Purcell is challenging the count.

"There are more houses here than last year, more activity here than last year. I'm not exactly sure how that (calculation) happened, but we'll challenge it like we did last year," Purcell said.

Population numbers are significant for communities that rely on revenue sharing.

Williams said the state's annual population count is based on what people list as their physical address when they apply for a state Permanent Fund dividend. The state in 1999 began requiring residents to give a physical address as well as a mailing address, Williams said. The number is cross-referenced with the most recent census -- in this case, the 2000 census -- to provide a more accurate count.