As a tool for fulfilling data needs for small area (subcounty) analysis, demographers are increasingly turning to administrative records such as building permits and tax assessor records as a source of data. While Census counts are considered to be the “gold standard,” administrative records provide a fine level of spatial detail and a valuable source of information for intercensal years. This analysis builds upon earlier research by comparing administrative records-based housing unit estimates developed during the 2000s decade with housing counts from the 2010 Census in San Diego County. Results show that both administrative records and Census counts have strengths and weaknesses that should be understood by the data user.
Increasingly sophisticated simulation modeling, used in infrastructure planning (e.g. transportation, water, sewer, energy), disaster response and emergency management, land use planning and resource conservation, requires increasing levels of detail for demographic and housing estimates.
For many years, population estimates and projections were made primarily at the national and state/provincial levels. In recent decades, they have been carried out at progressively lower levels of geography and are now routinely made for very small areas in the United States – census tracts, block groups, and traffic analysis zones. Methods are already designed for extremely small areas such as blocks and grid cells… We also note a growing demand for estimates and projections for even smaller areas such as tax assessor parcels, block faces, and street segments.The housing unit method ...may hold a strong advantage in subcounty population estimates. Other techniques of small area estimation require data, such as school enrollment, auto registration, and vital events records that are often unavailable at a subcounty level, and are delayed by a year or more in cases where the data are available. Therefore the housing unit method has the advantages of both availability and timeliness as compared with other data sources.
(Swanson and Pol 2005)
The method consists of a very basic premise and a series of simple equations:
Population = Household Population + Group Quarters PopulationThus, if four basic variables are known with certainty (total housing units, occupancy rate, average household size, and group quarters population) the total population of any given area can be known with certainty.
Household Population = Occupied Housing Units x Average Household Size
Occupied Housing Units = Total Housing Units x Occupancy Rate
This research focuses on the housing part of the equation...
The map, below, is part of a much larger presentation. The map shows over/under counts of housing by census tract in San Diego County, and was developed by comparing administrative records estimates to Census 2010
Full paper available upon request...