American Community Survey (ACS) Questions and Answers

  1. What is the American Community Survey (ACS)?

    The ACS is a household survey developed by the Census Bureau as part of the decennial program. It is a large demographic survey collected throughout the year using mailed questionnaires, telephone interviews, and visits from Census Bureau field representatives to about 3 million household addresses annually. Starting in 2005, the ACS produced social, housing, and economic characteristic data for demographic groups in areas with populations of 65,000 or more. (Prior to 2005, the estimates were produced for areas with 250,000 or more population.) The ACS will accumulate sample over three-year and five-year intervals to produce estimates for smaller geographic areas, including census tracts and block groups.

    It will take three to five years to accumulate a large enough sample to produce data for areas as small as census tracts and block groups. (See the chart below). Once that sample is collected the Census Bureau will release three- to five-year averages each year for those areas.

    Annual estimates are scheduled for release in the summer following the calendar year in which the data were collected as shown in the table below.

    ACS estimates release schedule
      Population size  
    of area    		   Reference  
    period    		 Data for the previous year
    released in the summer of:
    2003 2004 2005 2006 2007 2008 2009 2010+

    250,000+

    		 Annual
    estimates    		 X X X X X X X X

    65,000+

    		 Annual
    estimates    		       X X X X X

    20,000+

    		 3-year
    averages    		           X X X

    Census Tract
    and Block Group

    		 5-year
    averages    		               X

  2. When was the ACS started?

    The ACS demonstration period began in 1996 in four sites. In 1997, the survey was conducted in eight sites to evaluate costs, procedures, and ways to use the information. In 1998, the ACS expanded to include two counties in South Carolina that overlapped with counties in the Census 2000 Dress Rehearsal. This approach allowed the Census Bureau to investigate the effects on both the ACS and the census due to having the two activities going on in the same place at the same time. In 1999, the number of sites in the survey increased to 31 comparison sites. In 2000, the Census 2000 Supplementary Survey (C2SS) prototype for the ACS was conducted nationwide. From 2001 forward, the ACS has been conducted in all States.

  3. What estimates are produced from the ACS?

    Each year, the ACS produces estimates on characteristics of the population for the nation, States, and cities and counties with 65,000 population or more. Topics covered by the ACS are virtually the same as those covered by the Census 2000 long form sample data. Estimates are produced for demographic characteristics (sex, age, relationship, households by type, race, and Hispanic or Latino ethnicity), social characteristics (school enrollment, educational attainment, marital status, fertility, grandparents caring for children, veteran status, disability status, residence one year ago, place of birth, U.S. citizenship status, year of entry, world region of birth of foreign born, language spoken at home, and ancestry), economic characteristics (employment status, commuting to work, occupation, industry, class of worker, income and benefits, and poverty status), and housing characteristics (housing occupancy, units in structure, year structure was built, number of rooms, number of bedrooms, housing tenure, year householder moved into unit, vehicles available, house heating fuel, utility costs, occupants per room, housing value, and mortgage status and costs.

  4. How does the ACS compare with Census 2000?

    Census 2000 was a universe count of the population as of April 1, 2000. Approximately 1 in 6 housing units received a long-form survey version of the Census 2000 questionnaire, from which detailed demographic, social, economic, and housing characteristics were tabulated. The C2SS prototype of the ACS had a sample of 700,000 households, from which an annual average population figure was developed for 2000. The survey questions were similar between the C2SS and the long-form survey version of Census 2000, but there were minor differences in wording and design that may affect comparisons between the two. Both surveys utilized the new race and ethnicity categories developed for Census 2000. Both surveys were conducted principally by mail questionnaire, with telephone and personal visit collection for nonresponse follow-up.

  5. Does the ACS develop labor force estimates?

    Yes, the ACS includes questions about work and search for work so that some rough measures of labor force activity are available each year, along with the other social and economic data collected in the survey.

  6. How does the ACS compare with the Current Population Survey?

    The Current Population Survey (CPS), jointly sponsored by BLS and the Census Bureau, is a monthly sample survey of about 60,000 households designed specifically to produce the official monthly employment and unemployment data for the nation. The monthly CPS estimates are a key input to the Local Area Unemployment Statistics (LAUS) program conducted by BLS, which produces the official labor force statistics for States and substate areas.

  7. How does the ACS reference period relate to the reference period in the CPS?

    The CPS reference period is typically the week including the 12th of the month. CPS data are produced and published monthly. Annual average data are also developed at the end of the calendar year. The CPS uses a fixed reference period, as compared to the ACS, where the reference period is the week prior to when a respondent answers the survey. When respondents answer the survey varies throughout the month and year. Respondents are initially contacted by mail. If they do not return their survey within a month of receiving it, they are then contacted by phone. If respondents still do not provide answers, an interviewer then tries to contact them in person in the third month.

  8. Are there differences in the labor force estimates from the ACS and the CPS?

    In 2005, the numbers of persons the ACS classified as “unemployed” and “not in the labor force” for the nation were higher than the official CPS estimates. In addition, the number of persons the ACS classified as “employed” was lower than the official estimate from the CPS. The ACS unemployment rate was 6.9 percent, compared to the CPS annual average of 5.1 percent.

  9. Are there differences in the labor force estimates from the ACS and the LAUS program?

    Yes. In 2005, the numbers of employed individuals in the ACS were lower than in the LAUS estimates for nearly all States. Montana was the only State for which the ACS yielded a higher employment level than the LAUS program, +0.6 percent. Florida and South Dakota were the States with the largest relative differences, -5.7 and -5.4 percent, respectively, followed by Alaska and Hawaii, at -5.1 percent each. For the District of Columbia, the employment difference was -13.1 percent. ACS estimates of unemployment levels and unemployment rates were higher than the LAUS estimates in every State in 2005. Unemployment level differences ranged from less than +10.0 percent for Kansas and North Dakota (+5.7 and +7.1 percent, respectively) to more than +50.0 percent in Alabama (+83.8 percent), Hawaii (+58.4 percent), Florida (+58.1 percent), and Vermont (+50.4 percent). ACS unemployment rates were higher by just +0.4 percentage point each for Kansas and North Dakota, and ranged up to +3.3 points for Alabama. For the Commonwealth of Puerto Rico, the unemployment rate difference was +3.9 percentage points.

  10. What accounts for these differences?

    A number of factors may account for the difference in the estimates, including the following: overall questionnaire differences, differing requirements in the two surveys with regard to whether an individual is actively looking for work, and differing reference periods, modes of collection, and population controls.

  11. What are the questionnaire differences?

    The ACS questions relating to labor force activity are less detailed than those in the CPS. For example, the ACS uses only six questions in determining labor force status, while the CPS uses sixteen. There are more detailed, probing questions in the CPS regarding employment status. In addition, the CPS information is always collected by trained interviewers and never through mail questionnaires.

  12. How do the job search questions differ?

    The ACS instrument asks people if they are looking for work and available to a take a job if offered one, but does not ask about the nature of the job search. The CPS questionnaire probes to see if people are actively looking for work (interviewing, calling contacts, etc.) versus passively looking for work (for example, looking at want ads in the paper). In the CPS, a person is unemployed only if that person has actively searched for work.

  13. How can the ACS rolling reference period affect the estimates?

    ACS data are collected over a range of time periods. In the ACS, the reference is to activity in the “last week” whenever the respondent fills out the survey. In the CPS, the reference period is fixed for the calendar week including the 12th of the month. A varying reference week and time of data collection could be particularly problematic for shorter, transitory statuses or activities that could be influenced by seasonal variation. Unemployment, for example, is a state that frequently is quite transitory and subject to both seasonal and cyclical variability.

    ACS responses can relate to any weekly period throughout the year and reflect different economic events. Respondents can choose to delay completion of the ACS form.

  14. What is the mode-of-collection effect?

    The mode of collecting data also may affect the labor force estimates. All CPS interviews are conducted through personal visits or telephone calls by experienced CPS field representatives using laptop computers for data entry. ACS data are collected primarily by mail using “paper and pencil” questionnaires, with telephone and personal visit collection used as follow-up to mail nonresponse. Data collected using paper forms do not have interviewers assisting respondents in interpreting questions. They are more subject to respondents failing to follow questionnaire “skip” instructions properly, and are also subject to an increased probability of individuals not completing the survey than are interviewer-enumerated surveys.

  15. What population controls are used in the two surveys?

    Both programs utilize population estimates produced by the Population Estimates Program at the Census Bureau. The Population Estimates Program publishes total resident population and demographic components of change (births, deaths, and migration) each year. Also published are estimates by demographic characteristics (age, sex, race, and Hispanic or Latino ethnicity) for the nation, States and counties. The reference date for estimates is July 1st. The 2005 ACS estimates represent the population residing in households only; the population residing in group quarters is not included. The group quarters population is, however, included in the CPS.

  16. Does the LAUS program plan to utilize the ACS data in its estimating procedures?

    LAUS has no plans to utilize ACS data in monthly estimation. We are, however, investigating ways in which the ACS data can be used in place of the data from the decennial census long-form survey that are utilized in updates to program benchmarks every 10 years or so.

  17. Where can one obtain more information about the ACS?

    More information is available from the Census Bureau via American FactFinder or at the American Community Survey website.

 

Last Modified Date: June 6, 2007