The following data attributes are produced quarterly or monthly by the Prince William County GIS Division and other sources. If you are looking for the county's official demographic dataset, please see the Standard Data Dictionary.

*The population estimate for 2019 Quarter 2 is about the same as 2018 Quarter 4 due to the following:

• Updates to housing unit types and their associated occupancy rates and household sizes.
• The county's Group Quarters estimate was revised to 4,626 people (previous quarter was 5,267). 
• Instead of using Census PUMS (Public Use Microdata Sample) data from the  American Community Survey 5-Year estimates, the most recent 3 single-year estimates (2015, 2016, and 2017) were included to produce more up-to-date estimates for average household size and occupancy rates. Additionally, instead of only using PUMA 51244 and PUMA 51246 for the estimates, PUMA 51245 was also included (PUMA = Public Use Microdata Area). PUMA 51245 includes the cities of Manassas and Manassas Park but also covers areas in Prince William County adjacent to these cities. With these updates, occupancy rates for all household types slightly fell and average household sizes slightly rose from January 2018's estimates, with the exception of single family detached units. Therefore, the number of households fell slightly from Quarter 3 while the population rose.

Further Notes:

The county's housing occupancy rates and average household sizes are updated by housing unit type (single-family detached, attached, and multi-family) each year in late January. Thus, even though housing units may increase from the prior quarter, slight changes in the occupancy rate or average household size may result in fluctuations in the quarterly estimates that sometimes result in a small population decline (especially for Quarter 4 of each year when the stats behind the estimates are updated). Status changes in residential addresses and large multi-family developments resulting from occupancy permits also impact these estimates. If you are looking for annual population estimates, please click here.

NOTES:

• The quarterly estimates and annual estimates from 2010 to 2016 were restated in February of 2017 to reflect the markedly higher estimates generated starting at 2016 Quarter 3 by smoothing over prior estimates. For more information about these changes and corresponding methods, see the following PDF: Redistributing Quarterly Population Estimates, 2010-2016
  

• Compare PWC's estimates to the most current estimates and projections of PWC's population:
• U.S. Census ACS 1-Year Estimate (July 2017): 463,023
  
• Weldon Cooper Center (July 1, 2018): 463,046
  
• COG 2020 Projection (Round 9.1): 470,400
  

QUARTERLY ESTIMATE HISTORY *