Extracted from the U.S. Bureau of the Census web-site on the American Community Survey
In the past, the decennial census both counted the population (with the short form) and obtained housing, social and economic information by asking a portion of households to fill out the long form. Since this was done only once every 10 years, long-form information became badly out of date toward the end of each decade, so that planners and other data users were reluctant to rely on it. The American Community Survey will be an on-going monthly household survey that eventually will replace the census long form.
The survey, as part of the Continuous Measurement System, is a new approach for collecting accurate, timely information needed for critical government functions. This new approach will provide more accurate and up-to-date profiles of America's communities every year, not just every 10 years. Community leaders and other data users would have more timely information for planning and evaluating public programs for everyone from newborns to the elderly.
The American Community Survey will provide estimates of housing, social, and economic characteristics every year for all states, as well as for all cities, counties, metropolitan areas, and population groups of 65,000 persons or more.
For smaller areas, it will take two to five years to sample the same number of households as sampled in the decennial census. For example, for rural areas and city neighborhoods or population groups of less than 15,000 people, it will take five years to accumulate a sample the size of the decennial census.
Once the American Community Survey is in full operation, the multi-year estimates of characteristics will be updated each year for every governmental unit, for components of the population, and for census tracts and block groups.
The goals of the American Community Survey are:
To provide data users with timely, comparative housing, social, and economic
data throughout the decade about communities and population groups.
To aid federal, state and local officials in meeting their responsibilities
to administer and evaluate government programs.
To support sound decision-making by improving the quality of the
nation's information infrastructure.
Data users have asked for timely data that provides consistent measures for all areas. Decennial sample data are out-of-date almost as soon as they are published, about two years after the census is taken, and their usefulness declines every year thereafter. Yet billions of government and business dollars are divided among jurisdictions and population groups each year based on their social and economic profiles in the decennial census.
The American Community Survey can identify rapid changes in an area's population and give an up-to-date statistical picture when data users need it, not just once every ten years. Communities can use the data, for example, to track the well-being of children, families, and the elderly; determine where to locate new highways, schools, and hospitals; show a large corporation a town has the workforce the company needs; evaluate programs such as welfare and workforce diversification; and monitor and publicize program results.
The American Community Survey will be conducted using the best mail self-response techniques of the census combined with the techniques that allow surveys to produce high-quality data. For households that do not respond by mail, the quality of data will be improved by using a well-trained, permanent interviewer staff. This will provide the quality achieved by our current surveys staff using computerized interviewing, which incorporates edits into the collection instrument. Using a small permanent coding staff is expected to provide additional improvements in data quality.
As an on-going survey, the American Community Survey will be a flexible vehicle, capable of adapting to changing customer needs. Questions or specialized supplements can be added to the American Community Survey not only to collect new information, but also to help identify special populations or conditions.
The American Community Survey:
Uses the Master Address File (MAF), a complete listing of all residential
addresses in the country, for sample selection.
Mails or delivers American Community Survey questionnaires each month to potential
respondents.
Uses commercial vendor lists to obtain telephone numbers of mail nonresponse
addresses and conduct telephone interviews.
Upon completion of the telephone followup, selects a subsample of the addresses
still not interviewed and conducts personal interviews.
Improves the infrastructure for the Federal statistical system by providing
customized samples for subpopulations of interest, by providing the ability to
increase samples in the American Community Survey, and by providing a vehicle for
collecting sub-national data on supplemental topics.
The Census Bureau is currently developing a system to build and maintain a national Master Address File (MAF). The MAF will be initially constructed by a computer match of the U.S. Postal Service (USPS) Delivery Sequence File (DSF), the 1990 Census Address Control File (ACF), and the Topologically Integrated Geographic Encoding and Referencing (TIGER) files. Thereafter, periodic updates from the USPS DSF, census surveys and field listing activities will keep the MAF current.
The MAF can be created in an automated fashion for all areas that have city-style address systems where the mail is delivered using these addresses. For areas that do not have a city-style address system, the Census Bureau will create a MAF by conducting an address listing operation.
The MAF will be used as a sampling frame for the American Community Survey, as well as all of the Census Bureau's demographic surveys.
Each month, we will select a systematic sample of addresses from the most current MAF for the American Community Survey. The sample will represent the entire United States. Each monthly sample will be selected without repeating any addresses used for the American Community Survey in the previous five years. Consequently, no specific address will receive the ACS questionnaire more than once in any five-year period.
Larger proportions of addresses will be sampled for small governmental units (American Indian reservations, counties, and towns). The monthly sample size is designed to approximate the sampling ratio of Census 2000, including the oversampling of small governmental units.
The American Community Survey will be conducted using a tri-modal data collection operation to contact households. The three modes are:
Self-enumeration through mail-out/mail-back methodology;
Computer Assisted Telephone Interviewing (CATI); and
Computer Assisted Personal Interviewing (CAPI).
The self-enumeration procedure uses several mailing pieces: a prenotice letter, the American Community Survey questionnaire, and a reminder card. A replacement questionnaire will be mailed to addresses in the sample if the original questionnaire is not completed and returned to the processing office within the prescribed amount of time. For sample addresses that do not respond by mail, follow-up will be conducted through CATI, CAPI, or both.
The CATI operation will be conducted approximately six weeks after the American Community Survey questionnaire was mailed. We will attempt to obtain telephone numbers and conduct telephone interviews for all households that do not respond by mail. Census Bureau telephone interviewing staff will conduct these interviews.
The final data collection phase will consist of CAPI. Following the CATI operation, a sample will be taken from the addresses which remain uninterviewed. These addresses will be visited by Census Bureau interviewers, who will conduct personal interviews to obtain the information on the American Community Survey.
The American Community Survey is being implemented in four phases:
Demonstration period 1996-1998
Comparison sites 1999-2001
National comparison sample 2000-2002
Full implementation Nationwide 2003 and beyond
The ACS demonstration period began in 1996 and runs through 1998. In 1997, the survey was conducted in eight sites to evaluate costs, procedures and new ways to use the information. In 1998, the ACS expanded to include two counties in South Carolina that overlap with counties in the 1998 decennial census dress rehearsal. This approach will allow the Census Bureau to investigate the effects on both the ACS and the census of having the two activities going on in the same place at the same time.
In 1999-2001, the number of sites in the sample will be increased to 37 comparison sites and 8 phase-in sites in 1999 only. The phase-in sites will ensure that each Regional Office has sufficient workload to provide the experience needed to conduct the American Community Survey. The comparison with Census 2000 is designed to collect several kinds of information necessary to understand the differences between 1999-2001 ACS and the 2000 long form.
The comparison sites include various situations in which these differences are expected to be prominent. They were selected to have at least one site in each of 24 strata representing combinations of county population counts, difficulty of enumeration, and 1990-1995 population growth. The selection also attempts to balance areas by region of the country, and seeks to include several sites representing different characteristics of interest, such as racial or ethnic groups, highly seasonal populations, migrant workers, American Indian reservations, improving or worsening economic conditions, and predominant occupation or industry types.
The purpose of the comparison sites is to give a good tract-by-tract comparison between the 1999-2001 ACS cumulated estimates and the Census 2000 long-form estimates, and to use these comparisons to identify both the causes of differences and "diagnostic variables" that tend to predict a certain kind of difference.
In 2000-2002, pending Congressional approval of funding, plans are to add a national sample of 700,000 housing units per year to the ACS national sample. Starting in 2001, this will allow estimates to be provided for all states and for geographic areas or population groups of 250,000 persons or more.
From the national sample, direct comparison information can be used
to show how data from the American Community Survey compare with data
from the census long form for all states, large cities, and large
sub-state areas. For areas with fewer people, such as small counties,
small towns, or census tracts, statistical modeling will be used to
give indirect information telling how the ACS would typically compare
to the census long form "for an area like this." The model-based
comparison will use information from both the national sample and the
comparison sites, rather than just from the sample from each small
area.
In 2003, plans are to implement the American Community Survey in every county of the United States with an annual sample of three million housing units. Once the survey is in full operation, ACS data will be available every year for areas and population groups of 65,000 or more beginning in 2004.
For small areas and population groups of 15,000 or less, it will take five years to accumulate a large enough sample to provide estimates with accuracy similar to the decennial census. That means updated information for areas such as neighborhoods will be available starting in 2008 and every year thereafter.
An ACS goal is to provide data to the users within six months of the end of a collection or calendar year. For states, populous counties and other governmental units or population groups with a population of 65,000 or more, the ACS can provide direct estimates for each year. For smaller governmental units or population groups (those with a population of less than 65,000), estimates can be provided each year through refreshed multi-year accumulations of data.
Plans include the release of a microdata file each year patterned after the five percent Public Use Microdata Sample (PUMS) file of the 1990 decennial census records. The microdata file will allow for two different units of analysis: housing unit and person. The microdata file will include as many records as possible and show the lowest level of geography possible within confidentiality constraints. Users of the American Community Survey data can then customize tabulations to examine the information in the way that best serves their needs.
In addition, the ACS will provide summarized data for population and housing estimates, cross tabulated by various characteristics, down to the block-group level. The summarized data will be similar to the Summary Tape Files (STF) of the 1990 decennial census records, and are designed to provide statistics with greater subject and geographic detail than is feasible or desirable to provide in printed reports.
The microdata files, tabulated files, and associated documentation will be available on CD-ROM, as well as on this web site.
The ACS offers a number of features that can improve the Federal statistical system. They are:
Increased sampling options;
Flexibility in design and content; and
More frequent data for evaluation.
Because the current Federal statistical system is decentralized, surveys are conducted independently of one another. Each one must collect the same core data: number of occupied units, number of people, and the general characteristics of people. After these core data are collected, each survey focuses on its specific needs. The ACS can provide better estimates of the core data as well as provide a vehicle for collecting some specific survey data, thereby reducing this duplication.
The American Community Survey can also screen for households with specific characteristics. These households could be identified through the basic survey, or through the use of supplemental questions. Targeted households can then be candidates for follow-up interviews, thus providing a more robust sampling frame for other surveys. Moreover, the prohibitively expensive screening interviews now required would no longer be necessary.
State and local governments are becoming more involved in administering and evaluating programs traditionally controlled by the Federal government. This devolution of responsibility is often accompanied by Federal funding through block grants. The data collected via the ACS will be useful not only to the Federal agencies, but also to state, local and tribal governments in planning, administering, and evaluating programs.
Finally, the American Community Survey will provide more timely data for use in area estimation models that provide estimates of various concepts for small geographic areas. In essence, detailed data from national household surveys (whose samples are too small to provide reliable estimates for states or localities) can be combined with data from the American Community Survey to create reliable estimates for small geographic areas.