American Community Survey

American Community Survey

The American Community Survey (ACS) is an on-going, nationwide survey conducted by the United States Census Bureau. It is sent to a sample of the population and tells us what the population looks like and how it lives. The American Community Survey replaced the long form in the 2010 Decennial Census. The survey includes state- and local-level data profiles (both tabular and narrative) on demographic, social, economic, and housing characteristics.

The ACS in a Nutshell

  • The (ACS) is an ongoing survey
    The ACS provides data every year -- giving communities the current information they need to plan and to provide services. In addition, survey data help determine how more than $400 billion in federal and state funds are distributed each year.
  • Those surveyed include the resident population of the U.S. and Puerto Rico
    This includes all people living in housing units and group quarters. A “group quarters” is a residence that is managed by an organization providing housing or services for residents (e.g. college dormitories, prisons, and nursing homes).
  • The survey includes demographic, economic, housing and social characteristics
    The following characteristics are included in the survey: demographic, such as age & sex, race and relationship; economic, such as employment status, poverty, and health insurance coverage; housing, such as occupancy/vacancy status, units in structure and value of home; and social, such as ancestry, citizenship status and marital status. Visit the ACS website for the full list.
  • The (ACS) replaced the long form
    The ACS was distributed for the first time in 2005 and replaced what was once called the “long form.” The long form was completed every 10 years and collected the same information as the short form but also collected more detailed information such as income, education, and language spoken at home. The ACS collects detailed information every year rather than every 10 years. The decennial census is now the short form.
  • The ACS is a SURVEY, not a Census
    Unlike the Census 2010, which was filled out by everyone, the American Community Survey is filled out by just a sample of people in each community, and their answers are used to generate estimates that describe the entire community population. To make good estimates about the whole population, a sufficient number of people must be surveyed. For example, the survey responses of one person are not sufficient to make generalizations about even the smallest community in Virginia. Depending on the size of the community, a sample size of 100, 1,000, or even 5,000 people per year may be required.

Survey Basics: Understanding 1-year, 3-year and 5-year estimates

Note: Due to funding constraints, the U.S. Census Bureau has discontinued the 3-year estimates.

  • Sample Size
    • 1-year: all geographic areas
    • 3-year: areas with 20,000 or more
    • 5-year: areas with 65,000 or more
  • When to Use 1-year vs. Multi-year (3- or 5-year estimates)
    • Use 1-year estimates when:
      • Currency (timeliness) is critical
      • Researching large areas experiencing rapid change
      • Examining year-to-year changes
    • Use multi-year estimates when:
      • Reliability of the data is critical
      • Analyzing data for small areas (the 1-year sample sizes are too small to get a reliable base for estimates)
      • Studying smaller populations in large areas
      • Examining a set of areas in which some areas have only multi-year estimates

    For more information on when to use 1-year, 3-year and 5-year estimates, visit the U.S. Census Bureau website

  • Comparisons should be made on the same survey year

    ACS estimates based on data collected from 2005–2007 should not be called “2006” or “2007” estimates. Multiyear estimates should be labeled to indicate clearly the full period of time (e.g., “The child poverty rate in 2005–2007 was X percent”).

    The Census Bureau encourages comparing estimates based only on the same survey year(s). For example, suppose someone wanted to compare estimates for the city of Fairfax, which has a population of about 23,000, with estimates for Arlington County, which has a population of over 200,000 people. The ACS publishes 1-year estimates for Arlington County, but only 3-year estimates are currently available for Fairfax City. Thus, you should compare 2005–2007 estimates for Fairfax City with 2005–2007 estimates for Arlington County, even though more recent, single-year estimates are available for Arlington County.

    For more information on comparing estimates, visit the U.S. Census Bureau website

  • Release Dates
    New estimates are released every year for both data series. For example:
    • Data released in 2013 includes data collected in 2012 for 1-year estimates and from 2008-2012 for 5-year estimates
    • Data released in 2014 includes data collected in 2013 for 1-year estimates and from 2009-2013 for 5-year estimates
  • For specific release dates, visit the U.S. Census Bureau website.

ACS and the Decennial Census

10-year Census ACS
Purpose To show the number of people who live in the U.S. To show how people in the U.S. live
Length 10 questions 69 questions
Frequency Every ten years Ongoing
How it should be used To obtain counts of the population and their basic characteristics To learn about the population's demographic, economic, housing and social characteristics
Who is questioned The entire population (over 130 million households) A sample of the population (approximately 3 million households each year)
Type of data Counts Estimates (with margins of error)

Using Margin of Errors

Margins of error are provided for every ACS estimate. Ninety percent confidence intervals define a range expected to contain the true value of an estimate with a level of confidence of 90 percent. Margins of error are easily converted into these confidence ranges. For example, the 2006 ACS Data Profile for Virginia shows that 5,068,993 people age 25 and over resided in the state in 2006. By adding and subtracting the margin of error from the point estimate, we can calculate the 90-percent confidence interval for that estimate:

5,068,993 – 6,869 = 5,062,124 = Lower-bound interval
5,068,993 + 6,869 = 5,075,862 = Upper-bound interval

Therefore, we can be 90 percent confident that the true number of people 25 and over residing in Virginia in 2006 falls somewhere between 5.062 million and 5.076 million.