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In the famous quantum mechanics thought experiment known as Schrödinger’s Cat, the question concerns the status of a feline in a box with a flask of poison and something radioactive: Under some quantum theories, the cat is both alive and dead at the same time.
Fairfax County is Virginia’s Schrödinger’s Cat. In the annual population estimates from the Weldon Cooper Center for Public Service at the University of Virginia, the state’s largest locality is losing population. In the latest population estimates from the U.S. Census Bureau, it’s gaining population.
So which is it?
The answer is a bit more relevant than physicist Erwin Schrödinger’s hypothetical cat. Northern Virginia supplies 42% of the state’s general fund tax revenues. If the biggest locality in Northern Virginia (or anywhere else in the state) is losing population, that has financial implications statewide — and those implications become more significant the farther we get from the D.C. suburbs. Rural school systems get most of their funding from the state. In Scott County, 68% of that funding comes from Richmond, but much of that is Northern Virginia tax revenue that simply gets funneled through the state capital. That means property tax rates in Scott County are indirectly tied to the fate of Fairfax County — if Fairfax County starts shrinking, that’s less money that will find its way to Scott County, which means residents in that county along the Tennessee line would have to decide which they hate more, reducing what they spend on schools or paying more taxes.
The question of whether Fairfax is growing or shrinking has sometimes been a topic of debate in Northern Virginia, as well. It’s one that’s even more important in light of President Donald Trump’s downsizing of the federal government. “Draining the swamp” is all well and good, except that those of us living in counties that voted 70% or more for Trump are connected to that ecosystem, so let’s take a deeper look at the matter of Fairfax’s conflicting population figures.
First, we must acknowledge just how unusual — and recent — this question is. For most of its history, Fairfax County hasn’t just been gaining population, it’s been one of the fastest population gainers in the state. The last time Fairfax County lost population was in the 1830 census that said during the 1820s, the county had lost 19.3% of its population — so we’re now dealing with a situation that no one has seen for nearly 200 years. If it’s happening at all, that is. So is it?
Here are the conflicting numbers. The Weldon Cooper Center says that since the 2020 census, Fairfax County has lost 714 people — a decline of 0.1%. The Census Bureau says that since the 2020 census, Fairfax County has gained 10,633 — an increase of 0.9%.
In percentage terms, that’s not much difference, and even if the Census Bureau is right, that’s not exactly the kind of double-digit increase we’ve historically seen in Fairfax. Indeed, it’s more statistically akin to the feeble population growth that Fairfax recorded during the 1860s, during part of which Fairfax was in a literal war zone.
The numerical difference of 11,347 is more significant, though. That’s the equivalent of the size of Charlotte County. How do you miss that many people? Or imagine them?
The answer is how these figures are put together. While these are “estimates,” they are not estimates in the same way that I look out in the back yard and estimate that there sure are a lot of trees out in the woods. All these are based on data, just different data.
The Weldon Cooper Center relies on things such as school enrollment, driver’s license issuances and home construction to arrive at its annual estimates. The Census Bureau relies on tax returns and — significantly — its periodic series of surveys called the Community Survey. The bottom line: The Weldon Cooper Center uses more actual data and no surveys. Its estimates may be more conservative but are more grounded in facts. The Census Bureau also attempts to do something Weldon Cooper doesn’t: It tries to figure out how many people are immigrants. Put another way, the Weldon Cooper Center just tries to estimate the number of people; the Census Bureau tries to estimate the different types of people.
It’s that attempt to estimate the number of immigrants that makes the difference. Last year, the Census Bureau revised its methodology for estimating the number of immigrants. That resulted in what the bureau calls “a significantly higher” estimate of America’s immigrant population. Furthermore, the bureau applied that revised methodology retroactively, starting with estimates in 2021. The result is a much higher estimate for the number of immigrants moving into Fairfax County (and other places) during the Biden years — an estimate that may or may not be accurate.
The Census Bureau certainly believes it is, but the Weldon Cooper Center doesn’t show that immigrant surge appearing in the records it uses, when you’d think it would. That’s the essence of the discrepancy between the census estimates and the Weldon Cooper Center estimates. The Census Bureau believes that the number of immigrants moving into Fairfax County increased from 324 in 2020 to 16,376 in 2024. Immigration undoubtedly increased under President Joe Biden, but did it really increase that much? Whether you believe Fairfax County is growing or shrinking depends entirely on whether you believe the Census Bureau estimate on immigration, when other types of statistics aren’t suggesting that many people are moving into Fairfax.
I’m certainly in no position to adjudicate who’s right and who’s wrong, but at least now you know the reason for the different numbers. Even if the Census Bureau figure is right, or closer to right, it seems doubtful that these immigration numbers will continue under the stricter immigration policies of the Trump administration — so relying on immigration to make up for other population losses in Fairfax County may not be a long-term strategy.
It’s notable that the Census Bureau and Weldon Cooper agree on the other major trends reshaping the population in Fairfax County: Births outnumber deaths while the number of people moving out outnumbers the number of people moving in. The only difference is that the Census Bureau says that net out-migration doesn’t include immigrants, and Weldon Cooper says it does.
What the Census Bureau lists as “domestic migration” and Weldon Cooper categorizes as overall “migration” is also slowing in both reports, though still in the negative range. Weldon Cooper says that from 2020 to 2022, Fairfax County saw 26,200 more people move out than move in. For the most recent estimates, it says that from 2020 to 2024, the county saw 29,722 more people move out than move in — meaning that 88% of the county’s net out-migration took place in the first two years of the decade.
One of many questions looming over Fairfax County — and all of Virginia — is whether Trump’s government downsizing will spur a greater exodus from Northern Virginia and, if so, whether those who leave the region will settle elsewhere in Virginia or out of state. At the recent meeting in Alexandria of the special House of Delegates committee empaneled to gauge the effect of Trump’s cuts, there was testimony about people moving out of state to find work, but anecdotal examples, while fascinating, are not sufficient to build policy on.
If the goal for Virginia is to hope for a soft landing out of the federal cuts, then we would hope that the Census Bureau estimates of a big immigration surge in Fairfax County are correct, but prudence might dictate that we assume otherwise.
Either way, the big picture remains the same: The days of big population growth in Fairfax County are behind us, at least for now, and that has economic implications for Virginia, from Great Falls to the Cumberland Gap.
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