University of Virginia researchers project Prince William County’s population will reach a whopping 656,000 by 2040.
That’s about 100,000 more residents than county planners currently anticipate, but local officials dispute the university’s methodology used to calculate the projection.
“Historically, UVA demographics group projections have greatly exceeded our COG projections,” Prince William County Demographer Brian Engelmann said in an email, referring to the Metropolitan Washington Council of Governments or COG.
Prince William County’s planning department creates its projections in conjunction with the MWCOG every two to three years. Planners say the county’s population will reach 569,000 by 2040 -- 87,000 fewer residents than the 656,000 estimate from UVA’s Weldon Cooper Center for Public Service.
Weldon Cooper Center researcher Shonel Sen said the university generates population projections for all 133 cities and counties in Virginia using a uniform methodology to allow “apples-to-apples” comparison across localities.
“We acknowledge that local planners and administrators have more hands-on knowledge about their own localities and their scenario projections are just as valid,” Sen said. “Given that projections are inherently uncertain, as the future is largely unknown, numbers for the near future are more reliable.”
In 2017, Prince William challenged the Weldon Cooper Center’s population projections, calling its methodology “problematic” because it was based on population totals for the years 2000, 2010 and 2015.
“Because the county experienced a peak population boom between 2000 and 2010, using this period of time in addition to 2010 to 2015 growth generates a misleading assumption that the county will continue fast-paced growth up to 2040 and beyond,” Engelmann said.
Prince William County experienced an explosion of growth between 2000 and 2010, adding about 120,000 residents. Since then, growth has been slow but steady, adding an estimated 66,000 residents between 2010 and 2018.
Prince William County is the second-largest county by population in Virginia.
“We believe that population projections that take into account local land use patterns, construction trends, comprehensive plans and build-out analyses are more reliable,” Engelmann added.
Fairfax County, Arlington County and the City of Alexandria also challenged the Weldon Cooper Center’s population projections in 2017.
Qian Cai, director of Weldon Cooper’s Demographics Research Group, in a letter of response to Prince William County’s challenge, said the “true population in 2040 may be somewhere in between,” the two projections.
“As you can appreciate, the accuracy of projections declines quickly as years projected are farther away, similar to a one‐day vs. a 10‐day weather forecast,” Cai wrote.
But after reviewing the challenge submitted by Prince William County, the Weldon Cooper Center said its methodology used to develop the projections was “error-free” and declined to change the 2017 provisional population projections for Prince William County.
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