American Community Survey
The American Community Survey (ACS) is an ongoing statistical survey by the U.S. Census Bureau. It regularly gathers information previously contained only in the long form of the decennial census, such as ancestry, educational attainment, income, language proficiency, migration, disability, employment, and housing characteristics. These data are used by many public-sector, private-sector, and not-for-profit stakeholders to allocate funding, track shifting demographics, plan for emergencies, and learn about local communities. Sent to approximately 295,000 addresses monthly (or 3.5 million per year), it is the largest survey after the decennial census that the Census Bureau administers.
|American Community Survey|
|Participants||3.5 million households/year|
The United States Constitution (Article I, Section II) requires an enumeration of the population every ten years and “in such Manner as they [Congress] shall by Law direct.” From the first census in 1790, legislators understood that the census should collect basic demographic information beyond the number of people in the household. James Madison first proposed including questions in the census to to “enable them to adapt the public measures to the particular circumstances of the community.” Such knowledge collected with each census, he said, “would give them an opportunity of marking the progress of the society.  The number and type of questions included in censuses since 1790 have reflected current American societal trends and the growing nation’s expanded data needs.
By 1940, modernized statistical methods enabled the Census Bureau to start asking a sample of the population a subset of additional detailed questions without unduly increasing cost or respondent burden. In subsequent decades, questions that had previously been asked of all respondents, as well as new questions, moved to the subsample questionnaire form. As that form grew longer than the form sent to most households, it became known as the census “long form.”
Following the 1960 Census, federal, state and local officials, as well as the private sector, began demanding more timely long-form-type data. Lawmakers representing rural districts claimed they were at a data disadvantage, unable to self-fund additional surveys of their populations.  Congress explored the creation of a mid-decade census, holding hearings and even authorizing a mid-decade census in 1976, but not funding it.   
Efforts began again after the 1990 Census, when it became clear that the more burdensome long form was depressing overall census response rates and jeopardizing the accuracy of the count. At Congress's request, the Census Bureau developed and tested a new design to obtain long-form data. U.S. statistician Leslie Kish had introduced the concept of a rolling sample (or continuous measurement) design in 1981.. This design featured ongoing, month-by-month data collection aggregated on a yearly basis, enabling annual data releases. By combining multiple years of this data, the Census Bureau could release "period" estimates to produce estimates for smaller areas. After a decade of testing, it launched as the American Community Survey in 2005, replacing the once-a-decade census "long" form. 
The ACS has an initial sample of approximately 3.5 million housing unit addresses and group quarters in the United States, with sample selected from all counties and county-equivalents, American Indian and Alaska Native area, and Hawaiian Homeland, and in Puerto Rico annually. Data are collected primarily by mail, with follow-ups by telephone and personal visit. Approximately one third of those who do not respond to the survey by mail or telephone are randomly selected for in-person interviews. About 95 percent of households across all response modes ultimately respond.
Like the decennial census, ACS responses are confidential. Every employee at the Census Bureau takes an oath of nondisclosure and is sworn for life to not disclose identifying information. Violations can result in a 5-year prison sentence and/or $250,000 fine. Under 13 U.S.C. § 9, census responses are "immune from legal process" and may not "be admitted as evidence or used for any purpose in any action, suit, or other judicial or administrative proceeding."
The Census Bureau aggregates individual ACS responses (i.e. microdata) into estimates at many geographic summary levels. Among these summary levels are legal/administrative entities such as states, counties, cities, and congressional districts, as well as statistical entities such as metropolitan statistical areas, tracts, block groups, and census designated places. Estimates for census blocks are not available from ACS.
In order to balance geographic resolution, temporal frequency, statistical significance, and respondent privacy, ACS estimates released each year are aggregated from responses received in the previous year or previous five calendar years. The Census Bureau provides guidance for data users about which data set to use when analyzing different population and geography sizes.
From 2007 to 2013, 3-year estimates were available for areas with 20,000 people or more. This data product was discontinued in 2015 due to budget cuts. The last 3-year release was the 2011-2013 ACS 3-year estimates.
Current data releases include:
- 1-year estimates are available for areas with a population of at least 65,000 people. The 2015 ACS 1-year estimates were released in 2016 and summarize responses received in 2015 for all states but only the 26% of counties with 65,000 people or more. This is most suitable for data users interested in shorter-term changes at medium to large geographic scales.
- Supplemental estimates are shown in annual tables summarizing populations for geographies with populations of 20,000 or more.
- 5-year estimates are available for areas down to the block group scale, on the order of 600 to 3000 people. The 2015 ACS 5-year estimates, summarizing data from 2011-2015, were released in 2016.
ACS estimates are available via a number of online data tools. The American Fact Finder (AFF) is the primary tool for disseminating ACS data, allowing users to drill down to specific tables and geographies (starting with 2013 estimates, AFF also includes block group data). A selection of the most popular tables are shown in Quick Facts. Other tools include OnTheMap for Emergency Management, Census Business Builder and My Congressional District. My Tribal Area featuring 5-year estimates for federally recognized tribes, launched in 2017. The Summary File is the most detailed data source, and is available as a series of downloadable text files or through an API for software developers.
Custom cross-tabulations of ACS questions can be made using the Public Use Microdata Sample (PUMS), freely accessible through Integrated Public Use Microdata Series. PUMS data contain responses to every question from a sample of respondents. To protect respondent privacy, PUMS data are anonymized and only available down to areas containing 100,000 people or more known as Public Use Microdata Areas (PUMAs). The analysis of all ACS microdata without the sampling and anonymization in PUMS is restricted to qualified researchers at secure Federal Statistical Research Data Centers (FSRDCs).
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Those who favor the American Community Survey argue that census questions beyond head count have existed since 1790. All individual American Community Survey responses are kept private and are used (along with other ACS responses) to create estimates of demographic characteristics for various geographies. Because of data swapping techniques to ensure confidentiality, it is impossible to figure out how individual people responded based on data from published ACS estimates.
American Community Survey data provides important information that cannot be found elsewhere, and thus it is important that the ACS exists, as the federal government, as well as various businesses, researchers, and local governments use ACS data for planning and decision-making purposes.
The Department of Commerce has stated that those who receive a survey form are legally obligated to respond to the ACS. Those who decline to complete the survey may receive follow-up phone calls and/or visits to their homes from Census Bureau personnel. 13 U.S.C. § 221 imposes a fine of not less than $1000 for refusing or willfully neglecting to answer questions posed by census takers and a fine of not more than $5000 for willfully providing false information.
To date, no person has been prosecuted since 1970 for refusing to answer the ACS. Former Director of the Census Bureau Kenneth Prewitt remarked that the Department of Commerce is "not an enforcement agency" and that "the Department of Justice would have to do the prosecution, and we don't recommend that." The Census Bureau prefers to gain cooperation by convincing respondents of the importance of participation, while acknowledging that the mandate improves response rates (and thus accuracy) and lowers the annual cost of survey administration by more than $90 million.
The survey asks for more information, and at a higher frequency, than the simple enumeration required by U.S. Constitution Article I Section 2. Despite the GAO's conclusion that the Census Bureau has the authority to conduct the survey under 13 U.S.C. § 141 and 13 U.S.C. § 193, several U.S. representatives have challenged the ACS as unauthorized by the Census Act and violative of the Right to Financial Privacy Act. Rep. Ron Paul of Texas, who opposes the ACS, said of it that the founding fathers of the United States "never authorized the federal government to continuously survey the American people."
- US Census Bureau. "ACS Information Guide". www.census.gov. p. 8. Retrieved 2015-07-31.
- "The Founder's Constitution". The University of Chicago Press. Retrieved 19 June 2017.
- U.S. Census Bureau. "Through The Decades: Index of Questions". Retrieved 19 June 2017.
- U.S. Census Bureau. "1940 (Population) – History – U.S. Census Bureau". Retrieved 19 June 2017.
- "The American Community Survey: A Replacement for the Long Form? United States House Subcommittee on the Census of the Committee of Government Reform, 106th Congress (2000)." (PDF). Retrieved 19 June 2017.
- "Mid-Decade Census, Part 1: Hearings before the Subcommittee on Census and Statistics, 87th Congress (1961)". Retrieved 19 June 2017.
- "Mid-Decade Census: Hearings before the United States House Subcommittee on Census and Statistics of the Committee on Post Office and Civil Service, 89th Congress (1965)". Retrieved 19 June 2017.
- "Mid-Decade Census: Hearings before the United States House Subcommittee on Census and Statistics of the Committee on Post Office and Civil Service, 92nd Congress, first session on proposals for a mid-decade census of population and housing (1971)". Retrieved 19 June 2017.
- "13 U.S.C. 141(d)". Retrieved 19 June 2017.
- Alexander, Charles. "Still Rolling: Leslie Kish’s Rolling Samples and the American Community Survey" (PDF). U.S. Census Bureau. Retrieved 19 June 2017.
- US Census Bureau. "American Community Survey: Design and Methodology (PDF) p. 2-1." (PDF). Retrieved 19 June 2017.
- "ACS Design and Methodology. Chapter 2: Program History" (PDF). U.S. Census Bureau. Retrieved 19 June 2017.
- US Census Bureau. "Response Rates". www.census.gov. Retrieved 19 May 2017.
- US Census Bureau. "Is My Privacy Protected?". www.census.gov. Retrieved 2015-07-31.
- US Census Bureau. "Areas Published". www.census.gov. Retrieved 2015-07-31.
- U.S. Census Bureau. "When to Use 1-Year, 3-Year or 5-Year Data". www.census.gov. Retrieved 24 May 2017.
- Poole, Ken. "The ACS 3-year Demographic Estimates Are History". APDU: The Association of Public Data Users. Retrieved 2015-07-31.
- US Census Bureau. "American Community Survey Supplemental Data". www.census.gov. Retrieved 24 May 2017.
- US Census Bureau. "Data Tools Chart". www.census.gov. Retrieved 2015-07-31.
- US Census Bureau. "About PUMS". www.census.gov. Retrieved 2015-07-31.
- US Census Bureau. "Federal Statistical Research Data Centers". www.census.gov. Retrieved 2015-08-11.
- US Census Bureau. "Is the ACS Mandatory?". www.census.gov. Retrieved 2015-07-31.
- Selby, W. Gardner. "Americans must answer U.S. Census Bureau survey by law, though agency hasn't prosecuted since 1970". Retrieved 2015-07-31.
- US Census Bureau. "Census Bureau, Census 2000, Director Prewitt press briefing on March 30, 2000". www.census.gov. Retrieved 2015-07-31.
- US Census Bureau. "Mandatory vs. Voluntary Methods". www.census.gov. Retrieved 2015-07-31.
- US Government Accountability Office (April 4, 2002). "U.S. GAO – Legal Authority for American Community Survey, B-289852". Retrieved 2015-07-27.
- "None of Your Business!" by Ron Paul
- American Community Survey site at the United States Census Bureau
- ACS data from the Integrated Public Use Microdata Series
- American FactFinder – United States Census Bureau's Searchable Database
- Access to all survey questionnaires used from 1996 to 2011
- American Community Survey (ACS) User Guide for Disability Statistics
- US Code Title 13