Out of all large U.S. counties, Maricopa County is experiencing the 9th largest population growth, according to a new report from HireAHelper.

For the first time ever, California posted a population decline in 2020, and the United States as a whole didn’t fare much better. Its growth has decelerated to 0.35% year-over-year, the slowest growth rate since the Great Depression.


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Population experts blame the slowing growth rate on three big trends: families across the country are aging and having fewer kids, immigration policies have tightened up American borders, and economic hardships extending all the way back to the dot-com crash have shifted priorities away from marriage and families. While some contributing factors are down across the board, other social and economic factors have disproportionately impacted specific counties and states, exacerbating the problems for certain areas.

But Maricopa County is showing no signs of decline. The analysis found that in 2015, Maricopa County was home to 4,174,423 residents. 2020 Census data shows that there are now 3,825,183 residents in Kings County. Out of all large U.S. counties, Maricopa County is experiencing the 9th largest population growth. Here is a summary of the data for Maricopa County, AZ:

Metro: Phoenix-Mesa-Scottsdale, AZ

Percentage change in population since 2015: +9.7%

Percentage change in population since 2010: +19.7%

Total change in population since 2015: +404,658

Total change in population since 2010: +753,898

Population 2020: 4,579,081

Population 2015: 4,174,423

Population 2010: 3,825,183

For reference, here are the statistics for the entire United States:

Percentage change in population since 2015: +2.7%

Percentage change in population since 2010: +6.5%

Total change in population since 2015: +8,745,129

Total change in population since 2010: +20,156,980

Population 2020: 329,484,123

Population 2015: 320,738,994

Population 2010: 309,327,143

This latest decline in population growth at the national level is primarily the result of a lower birth rate and reduced immigration during the Trump administration. The U.S. birth rate has slowed for six years in a row to 11.4 births per 1,000 people in 2020—resulting in the fewest births since 1979, according to the Centers for Disease Control (CDC). From 2019 to 2020, the rate slowed 4%, which was twice as fast as the average slowdown since 2014. It was spread across all age groups of women, though the birth rate for teenagers aged 15 to 19 slowed 8%.

Meanwhile, the growth in immigration peaked in 2015, plateaued in 2016 at 3.3 immigrants per thousand residents, and has slowed markedly in line with new federal immigration policies implemented in 2017. The 2020 rate was down to 1.5 immigrants per thousand.

Since 2010, the population totals of only six states declined, and of those only West Virginia (down 3.7%) and Illinois (down 2%) dropped by more than 1%. It’s a different story over the last five years, though. In addition to West Virginia and Illinois, states losing 1% or more of their population were New York, Hawaii, and Alaska.

In West Virginia, the struggle is primarily with an aging rural population. There are more deaths than births in the state, and rural counties are shrinking nearly three times as fast as urban counties, according to the West Virginia Center on Budget & Policy. In Illinois, the population loss has accelerated for seven straight years, per Illinois Policy, due primarily to a lack of housing and employment opportunities, as well as high taxes.

Persistent population loss creates compounding economic, social, and political challenges for the residents who remain. West Virginia and Illinois are among just seven states that recently lost a congressional seat as a result of the 2020 Census population estimates. Other states losing a seat include New York, California, Pennsylvania, Ohio, and Michigan.

Zooming in on the county level, urban centers stand out for being hardest hit with population loss. CBRE Group research shows that urban centers were the only neighborhood type to see more people move out in 2020 than move in, and it underscores a trend that’s been a decade in the making.