Michigan's fastest-growing counties in 2018 were in the metropolitan regions of Detroit and Grand Rapids, according to yearly county population estimates released Thursday by the U.S. Census Bureau.

Meanwhile, populations elsewhere in the state particularly around Genesee County and in the Upper Peninsula were largely stagnant or declining.

Overall, the year-over-year county population estimates suggest Michigan is largely reshuffling its population, rather than bringing in many new residents. It's a trend all but certain to cost the state representation in Congress following the 2020 census.

"Millennials are looking for walkable, densely packed cities with all the amenities with restaurants and places to drink beer and all that," said Kurt Metzger, a demographer and director emeritus of Data Driven Detroit.

While Grand Rapids and Detroit appear to help with that, the newcomers are "young singles who are mostly coming from the suburbs and moving into Detroit," he said. "We're not bringing a lot of people from Chicago or Austin or places like that."

The six-county Detroit metropolitan area grew by about 4,700 residents as of July, remaining 14th largest in the nation at about 4.3 million people. Oakland and Macomb led that gain, adding more than 3,000 and nearly 2,800 people respectively. But their increases slowed by nearly 2,000 in Oakland and 500 in Macomb.

Washtenaw also showed signs of slowing with the addition of 1,800 people compared to 2017's 2,700.

Wayne lost residents last year — about 2,400 — but the decline was its smallest in two decades. Experts say this might reflect Detroit is nearing the end of an exodus tracing back to 1950. The U.S. Census Bureau will release city population numbers later this spring.

Wayne County’s loss was the 13th largest in the nation, but it was less than those in the home counties of other large Midwestern cities, including Chicago, Cleveland and Milwaukee.

Wayne County Executive Warren Evans said the trend of Michigan's most populous county underscores the importance of everyone being counted in the 2020 census.

"One day soon those numbers will grow," Evans said in a statement. "We must have an environment where people feel comfortable enough to be counted. We think that’ll be a big step to turning the corner and seeing the population numbers increase."

Genesee County lost nearly 800 residents, which also represented a slowing decline. Meanwhile, Saginaw declined by nearly 1,200 people, up from about an estimated 500 residents lost in 2017. Bay County decreased by close to 300 residents, which was about the same as the year prior.

The four-county Grand Rapids metropolitan area grew by more than 9,000 people to nearly 1.1 million residents. Kent had the largest increase of Michigan's counties with a gain of 4,555 people. Ottawa was second with nearly 3,600 residents added, the most since 2012. Barry and Montcalm also grew with 528 and 424 people respectively.

Nationwide, counties in the south and west saw the largest growth, including four Texas counties. And Dallas-Fort Worth-Arlington, Texas, had the largest increase of metro areas, a gain of nearly 132,000 in 2018.

To keep up, Michigan faces obstacles with an aging population and fewer births.

"Southeast Michigan is gaining population, albeit slowly, because we still have more births than deaths, and we are attracting immigrants," said Xuan Liu, manager of research and data analysis for the Southeast Michigan Council of Governments, in an email.

"Many of them came for education and knowledge-based jobs. But we are losing people domestically to other parts of the nation."

bnoble@detroitnews.com