The most populous counties continue to add residents in high numbers 

The latest U.S. Census Bureau population estimates released last month reveal that just over half of America’s 3,069 counties experienced population growth in 2016.

The most populous counties continue to add residents in high numbers; 84 percent of the 128 largest counties (those with a population greater than 500,000) experienced growth last year. The rate was slightly lower for the 821 medium-sized counties (with populations between 50,000 and 500,000 residents): only 71 percent of them saw their populations expand between 2015 and 2016.

In contrast, less than half (only 42 percent) of the nation’s 2,120 small counties (with populations less than 50,000) experienced growth.

Population continues to significantly concentrate in large counties. Counties with more than half a million-people added nearly 1.3 million residents in 2016, more than all the other counties combined. For the first time in the last four years, Maricopa County, Ariz. overtook Harris County, Texas in terms of number of residents added in a year: over 81,000 residents.

Pasco County, Fla. grew by more than 15,000 residents last year, pushing it over the 500,000-population threshold. The Florida county became the 128th large county in the country. Overall, the large county residents represent 49 percent of all counties, an expanding share among counties of different population sizes.

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Across the country, southern and western counties are expanding the most. For example, Texas counties added just over 430,000 residents last year, further driving population concentration in the South. Most of the fastest growing counties are also located in these regions. Of the 100 fastest growing counties, nearly half of them are found in Colorado, Florida and Texas. Almost half of the rapidly expanding counties are small. Idaho, South Dakota and Colorado. saw most of their small counties’ adding population last year.

While many pockets of the country showed signs of healthy population growth, others showed declines. Sixty percent of Midwestern counties and 65 percent of Northeastern counties took a population hit last year. This trend cut across different population sizes, but rural counties were more likely to register losses. Less than a fifth of counties in Illinois, New York, and West Virginia registered population increases last year. This trend remains consistent with prior years.