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Eureka saw the biggest gain in population among St. Louis County’s 88 cities while Florissant lost the most people, new U.S. Census population estimates released Thursday show.

The home of Six Flags gained 225 people from 2017 to 2018, followed by Richmond Heights, which added 176, and Kirkwood, 104.

Florissant, which remains the county’s biggest city, lost 167 people, followed by University City, 115, and Bellefontaine Neighbors, 104.

Ferguson bid goodbye to 70 residents between 2017 and 2018, according to the census estimates. Ferguson’s population has decreased by 540 people since 2010.

Unincorporated areas of St. Louis County gained 279 people.

St. Louis County Councilman Ernie Trakas, R-6th District, said a lower cost for government services may be a factor in why some people choose to live outside of the municipalities. Trakas’ district comprises mostly unincorporated territory.

“You’re getting services from the county in unincorporated, whereas if you live in Maplewood or Chesterfield you are getting it from them,” Trakas said. “It costs you more in terms of taxes and what have you.”

William Frey, a demographer with Brookings Institution in Washington, D.C., said the growth in the unincorporated portions of St. Louis County appears consistent with nationwide trends.

“In big cities, there have been declines in growth and then suburban areas are growing,” Frey said. “I see this as a greater dispersion of population and a spread-out of population.” It’s different from the beginning of the decade, Frey said, when more people were moving to cities.

One reason suburbanization might be coming back a little bit: younger adults.

“The housing market is coming back, the economy is coming back a little bit, and a lot of millennials who preferred to be in cities or who might have been stuck in cities are getting older, getting better economically and spreading out a little more.”

The village of Mackenzie, which had 131 people, voted to dissolve into unincorporated St. Louis County in last year’s April election. That dissolution, however, doesn’t affect the 2018 estimates because Mackenzie was incorporated for some of the time between the annual estimates, which are always done on July 1 of each year.

The dissolution will be reflected in next year’s unincorporated estimate.

Outside of St. Louis County, St. Charles city also grew considerably. The estimate puts the exurb city at 70,764 people, up 457 from the previous year.

Nationally, cities in the South and West grew the fastest. Some of that is because southern and western cities tend to be more sprawling than cities in the Midwest or Northeast, said Pew Research Center senior writer D’Vera Cohn.

The annual population estimates are not a survey; rather a collection of third-party data submitted to the census. Examples include births, deaths, IRS documents and Medicare numbers.

The real test of what’s changed will come in a couple of years when 2020 census data is released.

For now, the estimates are “the best we can do as we get toward the end of the decade,” Frey said.

Janelle O'Dea is a data specialist and reporter for the St. Louis Post-Dispatch.

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