Thanks largely to a continuing baby boom, Utah produced three of the nation's top 10 fastest-growing metropolitan areas last year, the Census Bureau reported Thursday.

The Provo-Orem metro area was No. 6 in the nation with 3.4 percent growth, adding an estimated 17,989 people between July 1, 2007, and the same date in 2008 — meaning it added the equivalent of a city with the population of Payson in a year.

The Logan metro area was No. 9 nationally with a 3.2 percent increase (adding about 3,917 people), and the St. George metro area was No. 10 at 3.1 percent (adding 4,142 residents). The nation has 363 separate metropolitan areas.

Census estimates show that about a third of such Utah growth came from people immigrating, likely attracted by economic conditions that were still generally better here than elsewhere. But about two-thirds of that growth came from Utah's much higher-than-normal birth rates (and long life expectancy).

"We have the highest fertility rate in the nation, and a lot of women in their child-bearing years," explained Utah state demographer Juliette Tennert. "It speaks to the fact that we have a culture here that places an important emphasis on families and children."

Pam Perlich, a research economist at the University of Utah, added, "We've got kind of a permanent youth movement to the state." She said each of the past 12 years have set a record for births here. On top of births to longtime residents, immigrants seeking work here tend to be young "and also are in their peak child-bearing years."

Helen Anderson, Provo community relations director, said of Provo: "It tends to be a conservative place politically, with high value on traditional marriage and children. … Not only do we have a high rate of births, but those children grow up and want to say close to home and continue to enjoy the quality of life here."

Tennert noted that the Census reported a few months ago that Utah was the fastest-growing state between 2007 and 2008. "So, of course, the smaller parts (like metro areas and counties) will show up high in the rankings, too."

Besides the three metro areas in the top 10 for growth, the Ogden-Clearfield metro area ranked No. 18 nationally with a 2.7 percent increase (adding 13,983 people). The Salt Lake City metro area ranked No. 59 nationally with a 1.9 percent hike (adding 20,330 residents — or the equivalent of the population of South Salt Lake in a year).

Also, Utah generated 10 of the nation's 100 fastest-growing counties: Rich (ranked 9th nationally), Piute (No. 17), Juab (28), Duchesne (38), San Juan (40), Tooele and Morgan (tied at 43), Sanpete (56), Utah (81) and Cache (87).

While Utah's economy was already beginning to slow down between 2007 and 2008, "It was still doing relatively well compared to other states. People were still moving to Utah to take advantage of the economic opportunities," Tennert said.

"For that time period, Utah's unemployment rate was 3.1 percent. And nationally, the average was 5 percent," she said. "Utah's economic opportunities are still better (than many areas'), so we still expect to have net in-immigration" in coming years despite the current economic recession.

As Perlich said, "Our economy is diversifying toward industries of growth. It's not like Michigan, and we're losing industrial base. … Even if we're losing jobs, we're not as bad as Michigan. Where are the people in Michigan going to go? They're going to come to places like this."

But data show that the real power behind population growth here is the local birth rate.

In fact, "natural growth" — the difference between births and deaths here in a year — is astronomical in Utah, according to the new Census estimates.

For example, it estimated that the Provo-Orem metro area gained 21 people per 1,000 residents from natural growth last year. That was second highest in the nation behind only Laredo, Texas. It was three times higher than the national average for natural growth of 6.2 per 1,000 residents.

And the other Utah metro areas were not far behind. Logan was No. 3 in the nation for its rate of natural growth at 20.7 per 1,000 residents; Ogden-Clearfield was No. 7 at 15.6; St. George was No. 11 at 15.0; and the Salt Lake City metro area was No. 14 at 14.1.

Estimates show, for example, that 62 percent of the growth last year in Provo-Orem was from "natural increase" and just 37 percent from immigration.

At other extremes, in the Salt Lake metro area 76 percent of growth came from "natural increase" and 24 percent was from immigration. In St. George, just 49 percent came from natural increase and 51 percent was from immigration.

Perlich said much of the current baby boom is an echo from a previous boom that peaked in 1982. "If you figure out how old those kids (from the 1980s boom) are now, they are in peak child-bearing years. We're on a 12-year run of record births. And it's an echo of that previous boom."

Anderson said that growth in Provo-Orem shows "this is a great place to live. We actually have been ranked highly through the last several years for having a high quality of life and low cost of living," and it has low crime rates. "Our families are growing. They want to stay here and live close to each other. We have the jobs, fortunately, to make that possible."

She said that Provo-Orem "can create jobs because we have two great universities — Utah Valley University and Brigham Young University. We have a strong entrepreneurial spirit here." Perlich said those universities also attract more young people, who have children while still in school and further increase the population.

Tennert said state officials are happy with the growth they see, which generally matches predictions they have made. "We always say that the economy fuels population growth, and population growth fuels the economy. We do think that it's a very positive thing."

Of course, it brings challenges for the future.

"We need to be thinking about infrastructure investment," Tennert said. "We need to make sure we can have transportation that can accommodate the population, and schools and services."

Tennert adds that the state expects growth from both immigration and natural growth to continue for years.

"We think we will continue to experience population growth that outpaces the national average," she said.