While the nation as a whole is aging and is projected to continue to do so for decades, almost 1 in 5 counties are getting younger. This recent trend has complex underpinnings but is driven largely by a rise in Hispanic populations.

According to July 1, 2017, population estimates released today, many counties in the Midwest, in particular, are showing a reversal in aging trends.

All in all, 531 counties across the country got younger since April 2010, the vast majority of them in a band that stretches through the Great Plains from Texas to Montana.

After seeing the median age in the region’s counties rise or stay the same during much of the 2000s, some counties in the Midwest have recently seen their median age decrease. In other words, they have been getting younger.

The “median age” of a population is the age at which equal numbers of people are above it and below it.

Of the Midwest’s 1,055 counties, 273 saw declines in median age between July 2010 and July 2017. It’s a big departure from the previous seven-year period — between July 2003 and July 2010 — when only 63 Midwestern counties saw declines in their median age.

This pattern of counties getting younger isn’t isolated to the Midwest. All in all, 531 counties across the country got younger since April 2010, the vast majority of them in a band that stretches through the Great Plains from Texas to Montana.

The youthful shift in these 531 counties is largely occurring alongside growth in their Hispanic populations, which typically are younger.

We see in Map 1 (where “NH” stands for non-Hispanic and “H” stands for Hispanic) that nearly all of the counties in the nation’s midsection with declines in median age also had increases in their Hispanic populations.

Indeed, the Hispanic population gain for these counties between April 2010 and July 2017 was 397,830 (a 21.6 percent increase). By comparison, the non-Hispanic population grew by 1.4 percent (208,037 residents) in the same counties over the same period.

The nation’s Hispanic population is young, with a median age of 29.3 compared with 38.0 for the country as a whole. Given that, it is no surprise that the median age is declining in counties with increasing Hispanic populations — especially if the median age was relatively high to begin with.

While most counties in the nation are getting older, the growth in Hispanic population, coupled with a surplus of births and net increases in international and domestic migration, have slowed and/or reversed aging patterns in a growing cluster of counties in the middle of the nation.

As a group, the 531 counties that got younger did so either because of net gains in international migration or natural increase (more births than deaths), which added 295,102 and 377,592 people, respectively. Net domestic migration resulted in a loss of 68,999 people but that varies quite a bit depending on the location of the counties (Map 2).

In the northern Great Plains, particularly in North Dakota, a large influx of domestic migrants led to increases in both the Hispanic and non-Hispanic populations. Natural increase fueled much of the change in the western parts of the Great Plains, particularly in Texas, Colorado, Nebraska and Montana. In more eastern areas, noticeably in Oklahoma, Kansas, Nebraska, Iowa, Minnesota, and North and South Dakota, net international migration was the main driver of this population change.

Along with these “reverse” aging trends, many more patterns can be discovered and explored in today's release Vintage 2017 Population Estimates by age, sex, race and Hispanic origin.

Luke Rogers is Chief of the Population Estimates Branch in the Population Division at the Census Bureau.