In addition to conducting a national census count every ten years, the United States (U.S.) Census Bureau produces annual postcensal population estimates. In cooperation with the National Center for Health Statistics (NCHS), the Vermont Department of Health (VDH) produces estimates by single year of age. VDH uses county and town estimates to create estimates for non-county geographies, such as Agency of Human Services and Health Department districts.
Vermont Insights acquired the single year of age data, produced from the U.S. Census Bureau’s 2010 Decennial Census and 2011-2014 postcensal estimates, from VDH. Postcensal estimates, by single year of age, were unavailable at the town and school supervisory union (S.U.) and district (S.D.) level. Only the 2010 Decennial Census population counts for these two geographies are presented in the report.
2010 Decennial Census
The decennial census is a ‘snapshot’ of the entire population at a single point in time. The U.S. Census determines how many people reside within the country’s borders, who they are, and where they live. Every 10 years since 1790, data from the decennial census have been used to apportion seats in the U.S. House of Representatives, as mandated by the U.S. constitution. The 2010 Census established the resident population of the United States as of April 1, 2010 and reported the basic demographic characteristic of the population such as age, sex, race and ethnicity. At the state and local level, the census provides critical data for decision making on such matters as education, employment, veterans’ services, public health care, rural development, the environment, transportation, and housing. It helps communities understand how they are changing.
For more information about the 2010 Decennial Census, see the U.S. Census Bureau’s website.
2011 – 2014 Postcensal Estimates
Each year, the U.S. Census Bureau produces and publishes estimates of the population for the nation, states, counties, state/county equivalents, and Puerto Rico. The U.S. Census Bureau estimates the resident population for each year by using measures of population change. The resident population includes all people currently residing in the United States. With each annual release of population estimates, the Population Estimates program revises and updates the entire time series of estimates from April 1, 2010 to July 1 of the current year. The U.S. Census Bureau develops estimates using a cohort component method, which is derived from the demographic balancing equation:
[Population Base + Births – Deaths + Migration] = Population Estimate
The population estimate at any given time point starts with a population base (the last decennial census or the previous point in the time series), adds births, subtracts deaths, and adds net migration (both international and domestic). For more information about the postcensal estimates, see the U.S. Census Bureau’s website.
U.S. Census Bureau and Data Confidentiality
Under Title 13 of the U.S. Code, the Census Bureau must keep data they receive confidential. The Census Bureau’s Disclosure Review Board oversees the disclosure of data and assures that confidentiality is maintained through a checklist of potential security risks that must be addressed. Specifically, the Census Bureau uses techniques known as disclosure avoidance to ensure that the data they provide are modified as needed to prevent the identification of any specific individuals.
Information that could directly identify an individual, such as name, address, social security number or telephone number is never shared by the Census Bureau. However, with statistical software, the possibility of deriving a person’s identity through cross-referencing data sets with small numbers exists, so the Census Bureau takes the added measure of using disclosure avoidance techniques to prevent this.
Some census tables have small counts which, in certain cases, may identify a specific individuals. However, disclosure avoidance techniques, such as data swapping, ensure these small counts are de-identified. Because of data swapping, when users see cells with numbers like one or two, those data cells do not represent actual people but rather statistical estimates of the number of people falling into a particular set of categories. Indeed, because those numbers are so small it is very likely that the precision of such estimates is relatively low and the actual value could be zero or some number significantly higher than one or two. For more information about data swapping and disclosure avoidance techniques, see the U.S. Census Bureau’s website.