Johnson and Story counties — homes to the University of Iowa and Iowa State University — are among Iowa’s fastest-growing counties, fueled in part by those relocating from other countries, according to data from the U.S. Census Bureau.
Statewide, Iowa’s urban areas continue to grow while rural populations decline.
Iowa’s State Data Center, which pulled U.S. Census Bureau data made public this week, shows estimated population changes between 2010 and 2015 in Iowa’s counties. The center said late last year that on a statewide level, Iowa’s population grew by 2.5 percent in that time to 3,123,899 residents. It ranks as the nation’s 30th most-populous state.
Gary Krob, coordinator of the State Data Center, said Friday that urban counties often have higher domestic and international migration numbers — which basically means more people are moving to those counties.
Polk County, Iowa’s most populous, had about 7,150 new international residents and more than 11,150 new domestic residents over the last five years.
The next closest in terms of migration numbers were Johnson and Story counties.
International migration Johnson County grew by 4,825 people, while Story County’s increased by more than 4,000 people.
“I’ve got to assume that a good reason for that, not the only reason but at least part of the reason, would be the universities,” Krob said. “Johnson County and Story County are both metropolitan areas, so on top of having the universities, they’re also more populated counties, that also helps contribute to migration.”
The international student population at the UI has more than doubled over the past decade, jumping from 2,189 in 2006 to 4,540 in fall 2015, according International Programs statistics. Some of the bigger increases began after the 2009 school year, when the 2,589 international student population swelled to 2,982 in 2010 and then to 3,463 in 2011. Annual increases of nearly 200 to more than 400 have continued.
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A majority of the UI’s international students come from China — numbering 2,797 in the fall, or about 62 percent of the total international enrollment. Other countries sending large numbers of students to Iowa include South Korea and India.
Johnson County also brought in nearly 2,400 new domestic residents since 2010, while Story County lost almost 50 on that front.
Linn County saw an increase in international migration of more than 1,770 people, while domestic migration added 1,160.
Krob said Iowa has seen roughly a 25-year trend in which rural counties see populations drop while urban counties get bigger.
Between 1990 and 2000, about 45 Iowa counties had dropping populations. From 2000 to 2010, that number grew to about 75, where it has stayed, Krob said.
“Without going back in the ‘90s to find out exactly where the tipping point is, I think we started seeing some of that then and it’s just progressed from there,” Krob said.
Some Eastern Iowa communities have been trying to take advantage of their recent growth through special census counts to boost their annual Road Use Tax dollars, which are distributed on a per capita basis.
North Liberty’s special census was finalized earlier this month. The final count came in at just under 18,300 residents. North Liberty’s median age is 30.2 and nearly 30 percent of the city’s population is under 18.
Marion officials began their special census counts earlier this month.
Vanessa Miller of The Gazette contributed to this report.
Iowa’s five fastest growing counties
Dallas: 21.1 percent
Johnson: 10.2 percent
Polk: 8.6 percent
Story: 7.2 percent
Warren: 5.2 percent
Counties with the highest percentage drop in population
Fremont: 7.2 percent
Adair: 5.9 percent
Adams: 5.8 percent
Audubon: 5.7 percent
Emmet: 5.2 percent
Iowa 2015 population facts
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Polk County had the highest net migration, with 18,305 new residents including domestic and international.
Clinton County had the biggest negative numerical change in population from 2010-2015, dropping by nearly 1,350 people.
Adams County is the only Iowa county with a population of less than 5,000. The county has 3,796 residents.
Polk County is Iowa’s most populous, with 467,711 residents.