Scouring the plethora of numbers in the 2020 Census could break a person.
When the data were released last month, one of the numbers for Prince William County and its towns last month didn’t seem to fit with the rest.
Northern Virginia’s population rose by 14.3%, and the combination of Prince William, Manassas and Manassas Park rose by 19.3%. Dumfries jumped by 14.5%, Occoquan increased by 10.8% and even tiny Quantico rose by 20.4%.
But amid all the increases, Haymarket showed a relatively drastic decrease of 13.3%, or 237 residents, from 1,782 in 2010 to 1,545 in 2020.
Haymarket was one of only three incorporated towns in Northern Virginia shown to lose residents, joining Clifton and Middleburg.
So are Haymarket’s numbers correct? At least one demographer says mostly, but it’s complicated.
Census data is broken down in several different categories at a variety of geographic areas, including state level, locality, congressional districts and magisterial districts.
Numbers are also broken down in what is called blocks, block groups and tracts. Blocks are the smallest dataset and can, as the name suggests, cover just a block. A connected set of those is combined into block groups, which are then grouped into tracts.
Researchers have been sounding the alarm over new methods used in the 2020 Census that have blurred numbers as the data is examined in smaller geographic areas.
The problem with the 2020 data has been that a computer algorithm places people where they don’t actually live and scrambles some age and racial demographics to protect privacy. Researchers say the method doesn’t affect the numbers at the larger geographic area, but can cause issues as the dataset gets smaller and smaller.
Hamilton Lombard, a demographer with the University of Virginia’s Weldon Cooper Center, pulled the Census tracts and blocks for Haymarket, Clifton and Middleburg and compared the numbers to 2010.
Clifton lost 39 residents and Middleburg lost four, which Lombard said seems to be symbolic of the problems with numbers in small areas.
In Haymarket, however, one particular tract stood out, so Lombard used county real estate records and satellite imagery to examine the area. Based on that look, it appears that although Haymarket may have been affected somewhat by the algorithm, it was overcounted in 2010 by showing nearly 200 people living on vacant land.
Lombard said it appears the 2020 Census corrected the 2010 mistake, contributing to the reduction in population.
Haymarket’s town limits are shaped like a rectangle centered around Va. 55. A small sliver of the town is on the north side of Interstate 66 and includes half of the Haymarket park-and-ride lot and the I-66 interchange with U.S. 15.
The area in question is at the interchange. County real estate records show an approved subdivision of roughly 27 parcels off Old Carolina Road. Five homes have been constructed on six parcels and, based on county records, were built long before the 2010 Census.
Lombard said the 2010 Census showed nearly 200 people living in that undeveloped area, and it’s extremely unlikely that a housing development that existed in 2010 was bulldozed.
The only visible changes to the area between January 2012 and June 2021 satellite images are a larger interchange and the park-and-ride lot.
Lombard said the situation in Haymarket, unfortunately, is more of the exception than the rule with population counts in small towns.
“This is kind of a pleasant surprise,” he said.