South Dakota got a mention in a news release issued last week by the U.S. Census Bureau. That's because the state is home to several counties that show an estimated decrease in median age between 2010 and 2017.

The bureau headlined its news release with the highlight: "Midwest Home to Most of the Counties With Decreases in Median Age."

But even if 43 of South Dakota's 66 counties showed an estimated decrease in median age, the counties with higher populations generally showed increases. That gave the state as a whole an increase in estimated median age between 2010 and 2017.

For the whole state, the South Dakota median age is estimated to have increased between 2010 and 2017, from 36.9 to 37.1 years. That's younger than the median age for the U.S. which is estimated to have increased between 2010 and 2017, from 37.2 to 38.0 years.

The bureau's news release led with the fact that just 17 percent (531) of counties nationwide saw an estimated decrease in median age between 2010 and 2017. (The median age is the age that splits a population into two equal groups – half are younger than the median age and half are older.)

And of those 531 counties, a smidgen more than half – 51.4 percent – are in the Midwest, according to the bureau.

The news release quotes Molly Cromwell, a demographer with the bureau: "The majority of the counties getting younger were in the Midwest, and of these counties with 10,000 people or more in July 2017, some of the largest decreases were in North Dakota, South Dakota and Nebraska," said Cromwell. "Williams County, N.D., had the largest decrease in median age, declining by 7.1 years."

In South Dakota, Sanborn was the county with the greatest decrease in median age between 2010 and 2017. For that period, Sanborn's median age is estimated to have dropped by more than seven years (-7.4). Sanborn's estimated population in 2017 was 2,450.

Rounding out the top 10 South Dakota Counties for estimated median age decrease between 2010 and 2017 are: Clark (-5.4); Walworth (-3.6); Beadle (-3.5); Hutchinson (-3.4); Haakon (-3.3); McCook (-3.2); Jerauld (-2.8); McPherson (-2.8); and Faulk (-2.5).

Of the top ten counties for estimated median age decrease, the only one with more than 10,000 estimated population is Beadle County.

Of the five South Dakota counties with an estimated population of more than 30,000, only Brown County has an estimated decrease in median age (-1.4).

Measured by sheer numbers, the general trend is that South Dakota counties with higher populations are estimated to be growing, while counties with smaller populations are estimated to be losing population. Both Brown and Beadle are estimated to have grown in population from 2010 to 2017 – Brown by about 7 percent and Beadle by about four percent.

Counties Brown and Beadle show there's not a strictly uniform pattern for growing, higher population counties to get older.

South Dakota's state demographer, WeiWei Zhang, who's assistant professor of sociology at South Dakota State University, told the Capital Journal there's likely a somewhat different story for every county that accounts for the change in estimated median age.

Zhang's observation about the newly released figures from the U.S. Census Bureau: "There's a lot of variation."

To get a clearer idea of what's going on in a particular county, Zhang said, it's important to look at the components of population change – whether it's due to a greater number of births than deaths or whether it's due to immigration of younger families into the county, or both.

In the case of Beadle County (county seat Huron), Zhang said, the number of under-18 residents was estimated to have increased by 800 from 2010 to 2017, which is a large percentage increase. She said Beadle County has seen a lot of Asian and Hispanic immigrants.

Asian immigration to Beadle County is accounted for by workers who come from Karen (a state in Myanmar).

The median age estimates from the U.S. Census Bureau were released as part of a broader set of estimates including ethnicity. The bureau releases estimates annually in a regular cycle through the year, which includes estimates of state and county populations, followed by estimates for cities and housing units.

A census – a count of population, not an estimate – is conducted every 10 years. The next census comes in 2020.

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