2020 census shows Iowa urban areas grow, but population decline continues in rural areas

Iowa’s population grew 4.7 percent from 2010 to 2020, according to Census Bureau data released Thursday, with nearly 80 percent of the growth happening in the state’s four largest counties — while 68 counties posted population losses.

Overall, census data showed Iowa grew by 144,014 people since the 2010 count, exceeding the 4.1 percent increase of 120,031 in the first decade of the 21st Century.

Growth was concentrated in and around the urban centers of Polk, Johnson, Linn and Scott counties. The fastest growing county was Dallas, west of Des Moines, with an increase of 50.7 percent (33,543). Johnson was the state’s second-fastest growing county, at 16.8 percent (21,972 people). Polk grew by 14.3 percent (61,761), Linn by 9 percent (19,073) and Scott by 5.7 percent (9,445).

“In a way, it’s really sort of the same old story that the state, overall, is growing a little bit,” said David Peters, an Iowa State University sociology professor. “But even though as a state we're growing, it kind of masks a lot of unevenness. So you have phenomenally fast growth rates in the state’s large urban centers and an exodus of people in most of rural Iowa.”

According to the census data:

• Tiffin had the highest rate of growth in the state — 131.7 percent. Growth in its Johnson County neighbors of 53.1 percent in North Liberty and 48.2 percent in Solon helped fueled the county’s growth rate. Coralville’s and Iowa City’s population grew at lower rates — 18 and 10.3 percent respectively — but well above the state average.

• To the north in Linn County, the rate of growth was spurred by Palo (37.1 percent), Fairfax (33.2 percent) and Cedar Rapids (9 percent, bringing the city’s population to 137,710 people).

The new data also showed Iowa becoming more diverse, with an increase in the number of Black and Hispanic Iowans equal to about three-quarters of the overall growth. Still, 2,694,521, or 84.5 percent of Iowans, identified as “white alone.” But that’s down from 88.7 percent 10 years earlier.

Iowa’s Hispanic numbers increased 64,442 to 215,986, from 5 percent in 2010 to 6.8 percent today. Nationally, Hispanics are 18.7 percent of the population.

Ten years ago, Blacks were 2.9 percent of Iowa’s population. That’s up to 4.1 percent, an increase of 43,628 to 131,926. Nationally, Blacks are 12.4 percent of the population.

The change in diversity can be seen in various ways, including in what the Census Bureau calls its diffusion score, an indication of how diverse and unconcentrated the population is relative to the three largest racial and ethnic groups. Iowa’s diffusion score rose from 3.5 to 6.5 percent over the past decade, while the nation’s rose from 7.7 to 11.4 percent.

The five counties with the highest diversity indexes — Buena Vista, Crawford, Woodbury, Marshall and Polk — did not change from 2010 to 2020, but the probability that two people chosen at random in any of those counties will be from different race and ethnic groups increased. In Buena Vista County, for example, the diversity index increased from 48.4 to 61 percent.

Although the number of minorities grew, ISU’s Peters noted that it wasn’t in areas that previously saw an influx of Hispanics. Louisa, Crawford and Marshall counties that had seem growth in previous counts showed overall population losses of 4.8. 3.3 and 1.3 percent, respectively.

Although growth was clustered around cities, not all urban areas made gains. Black Hawk County, the state’s fifth largest and home to Waterloo with 131,144 people in the latest census, lost 54 residents over the decade. The population of Cerro Gordo County, home of Mason City, dropped by 2.3 percent (1,024).

Only a handful of rural counties, mostly in northwest Iowa, saw population increases.

Population gains ranged from six in Cedar County to 61,761 in Polk while losses ranged from 56 in Carroll County to 2,656 in Clinton County.

The least populous county is Adams County, in southwest Iowa, which has 3,704 people — a decline of 8.1 percent or 325 people. Polk County continued to have the most people with 492,401, a 14.3 percent increase of 61,761 people. It also is the most densely populated county, with 860.5 people per square mile.

The new population data comes with political implications that will drive policy decisions, Drake University political scientist Dennis Goldford said Thursday.

Democrats are “incredibly dependent” on votes in the six largest counties. Now retired U.S. Sen. Tom Harkin won reelection in 1996 and Tom Vilsack, now the U.S. agriculture secretary, was elected governor two years later by carrying the largest counties by wide enough margins to offset losses in rural Iowa. More recently, Republicans have flipped that script.

Republicans have largely been the party of rural Iowa and suburbs. It may not be a fair representation of Democrats, Goldford said, but they are seen as the party of cities.

“It’s not that Democrats are ignoring rural Iowa,” Goldford said. “Their problem is to figure out rural Iowa. They don’t have to win, but they can’t lose so badly” if they hope to win statewide races and U.S. House seats.

The new population numbers will be used to redraw U.S. House and Iowa legislative districts. Iowa uses a nonpartisan redistricting process that must be approved by the Iowa Legislature.

Iowa won’t lose any of its four congressional districts, but the loss of people in rural Iowa and gains in cities likely will result in significant changes of the boundaries of those election districts.

Republicans represent the 1st and 2nd districts despite Democratic voter registration advantages there. In the 4th, the GOP has over 81,000 more active voters than the Democratic Party.

Goldford speculated that Democratic U.S. Rep. Cindy Axne in the 3rd District may be most affected by redistricting. In 2020, she was reelected by running up her margin in Polk County while losing the other 15 counties in the district.

“Because Iowa’s not losing a district, redistricting will tinker around the edges,” he said. “Tinkering sounds minor, but if you’re on the edge — like Axne — you’re vulnerable.”

Comments: (319) 398-8375; james.lynch@thegazette.com

John McGlothlen of The Gazette contributed to this report.