General Information

The American Community Survey is the ambitious new national survey from the U.S. Census Bureau that is replacing the long form portion of the decennial census. While some version of this survey has been in the field since 1999, it was not fully implemented in terms of coverage until 2006. In 2005 it was expanded to cover all counties in the country and the 1-in-40 households sampling rate was first applied. However, persons living in group quarters (such as nursing homes, dormitories and prisons) were not added to the survey until 2006. (The original plan was to begin GQ coverage in 2005 but last-minute budget reductions delayed it for a year.) The full implementation of the (household) sampling strategy for ACS entails having the survey mailed to about 250,000 households nationwide every month of every year and was begun in January 2005. In January 2006 sampling of group quarters was added to complete the sample as planned (albeit several years later than originally planned.) In any given year about 2.5% (1 in 40) of U.S. households will receive the survey. Over any 5-year period about 1 in 8 households should receive the survey (as compared to about 1 in 6 that received the census long form in the 2000 census). Unfortunately, receiving the survey is not equivalent to participating in it, since the Bureau has adopted a strategy of sampling for non-response. This results in something close to a 1 in 11 households actually participating in the survey over any 5-year period.

Data Release Plan Based on Size of Geographic Area

Data based on the ACS surveys for any calendar year will be published in the late summer of the following year for geogrpahic areas with a minimum of 65,000 population. For smaller areas the Bureau will only publish data based on surveys for multiple consecutive years as follows:

• For geographic areas of 20,000 or more population data will be published based on 3 consecutive years of survey data. Thus, for example, the first time we saw data tabulated for Jefferson City, MO (population around 40,000) was in December of this 2008 and it was based upon the surveys done in 2005 through 2007. In late 2009 data will be released based upon the surveys taken in 2006-2008, etc.

• For geographic areas with populations under 20,000 (down to the block group level, but NOT to the block level) data will be published based on 5 consecutive years of survey data. Thus, for example, data for the majority of counties in northern Missouri, for 46 out of 53 counties in the state of North Dakota, and for all census tracts and block groups everywhere, data will first appear some time late in 2010 and will be based upon the combined survey data of 2005 through 2009. New data for these areas should then be published each year, based upon the most recent 5 years of surveys. Even if a census tract should happen to meet the population threshold of 20,000 (which is rare) no data will be published for it other than the 5-year "period estimates". Similarly, data at the ZIP code/ZCTA level will only be published as 5-year period estimates, even though there are many ZIP codes that meet the 20,000 threshold.

Currently Available Data (see revision date, above)

To access the data (and extensive metadata) within the MCDC data archive go to the ACS section of the Uexplore/Dexter home page.

Prior to the 2005 survey year the only data available from the ACS are for selected geographic areas with a minimum of 250,000 population. Beginning with 2005 data there are data for geographic areas of 65,000+ population. These data can be accessed via the Census Bureau's American FactFinder web application. For the MCDC online data archive we began downloading and converting ACS data starting with the 2005 results (released in 2006). We are providing access to the ACS summary data (base tables, profiles and our own custom extracts -- all but the PUMS data) for each year in separate uexplore-able data directories as follows:

- acs2007

- acs2006

- acs2005

What To Expect in the Coming Two (or more) Years

You can expect to see an acs2008 data directory appear in the third quarter of 2009, with single-year data appearing around September, and 3-year period estimates in December. Expect an acs2009 directory to be created in the third quarter of 2010, with single-year data for 2009, 3-year period data based on 2007-2009 and, for the first time, 5-year period estimates data (down to the tract and block group levels and based on 2005-2009 survey years ). These 5-year data are probably not going to be available until around January, 2011. It should be great fun to compare the population counts in these data sets, which are based on a complex sampling and weighting scheme, with the corresponding numbers that will become available when the Public Law 94 files are released on April 1, 2011 (this release data is mandated by law and is also known as the redistricting file.) It is not known for certain whether these data will use the 2000 or the 2010 census geography (tract and block group definitions).

For those who want to think even further ahead, in 2011 we should start to see ACS data being released that will be based, at least in part, on 2010 census population controls rather than inter-censal county estimates. We can expect to see the small-area data using these figures released in very late 2011 or early 2012. Of course, since these are based on 5 years of data we are not sure if some of the years will use the old weighting scheme (we really don't know the population or housing unit counts for 2009 based on the 2010 census, after all) or something recalibrated to reflect what we know from taking the census.

ACS Data Profiles

Both the Census Bureau and the Missouri Census Data Center provide data profile reports (and corresponding data files) containing highlights of the very detailed information contained in the complete set of base tables. The Bureau profiles can be accessed via American FactFinder. The MCDC profiles can be accessed in various ways. A good starting page allows you to select up to 4 geographic areas and any or all of 4 profiles (Demographic, Economic, Social and/or Housing) and have those areas displayed as columns in a single table. Click here to see an example of the MCDC Economic and Social profiles for 4 selected geographic areas.

Techie note: Uexplore/Dexter users should be aware that all the data for the entire country for 2006 and 2007 used to generate these profiles are contained in a single archive data set per year (actually, in two data sets for 2007: one for the single-year data and one for the 3-year data). A link at the bottom of the profile page takes you directly to the dexter application for accessing these data files (e.g., acs2007.usmcdcprofiles.sas7bdat and acs2007.usmcdcprofiles3yr.sas7bdat).

PUMS Data

The ACS also includes a public use microdata sample (PUMS) product. We plan to keep all such datasets (regardless of year) in the acspums data directory. We currently have data for 2004 (entire-US datasets only) and for 2005 thru 2007 (state level datasets). This collection will only be of direct interest to researchers with access to and knowledge of how to use a statistical software package.

PUMAs (Public Use Microdata Areas) Related to ACS

Users of this web site will notice that we place considerable emphasis on data summarized at the PUMA geographic level. This is because PUMAs are large enough (100,000 minimum population) that they qualify to have new single-year ACS data published each year. We can use PUMA data therefore to look at trends and maps that cover the entire state. We have created custom reports to help users understand where these PUMAs are (what counties and cities they contain or in which they are contained) together with links to pdf map files showing them (see our Geographic Reference Reports, the first 3 bullets). To learn more see the discussion of PUMAs that appears in our introductory Ten Things to Know About the American Community Survey page (cited just below).

Where to Get More Information

There has been and continues to be a lot written about the ACS. Here are a few of the best resources.

• American Community Survey Home Page at the Census Bureau. This is the official site. Comprehensive, with many links to the various components.

• The ACS Compass Products page at the Burea's ACS web site provides links to a series of educational meterials related to the ACS. Includes handbooks, power point tutorials and other materias, which seem to be appearing almost every few weeks. The Compass Handbooks are all targeted to specific audiences and have titles such as What General Data Users Need to Know, What the Business Community Needs to Know, etc.

• ACS Section of MCDCs Product Inventory Showcase points to various items on this site related to the ACS.

• Ten Things to Know About the American Community Survey is a locally produced introductory document that focuses on things that new users will need to know in order to make use of this important data resource. (Parts are specific to the 2005 edition of the data.)

• Population Bulletin on The American Community Survey from the Population Reference Bureau is an excellent in-depth review of the survey (written in September, 2005) . This is a 20-page pdf document.

• Q & A's About the ACS - powerpoint presentation by Cynthia Taeuber and Dave Hubble, Census Bureau. Adapted for presentation at the 2004 MCDC annual meeting by John Blodgett and Ryan Burson. 54 slides. Gets down to some of the statistical nitty gritty of the ACS.

• ACS FAQ for Media from the Census Bureau's PIO, May, 2005. MS Word document, 5 pages.

• See also the Docs subdirectory of the MCDC's (this) acs data directory.

There is a mailing list you can subscribe to that sends out "ACS Alerts" with the latest news about the ACS. See the Bureau web page for more information. The alerts are also posted to the ACS web site.