Documentation: ACS 2007 -- 2011 (5-Year Estimates)
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Publisher: U.S. Census Bureau
Document: The 2007-2011 ACS 5-Year Summary File Technical Documentation
citation:
Social Explorer; U.S. Census Bureau; American Community Survey 2007-2011 Summary File: Technical Documentation.
The 2007-2011 ACS 5-Year Summary File Technical Documentation
1. Introduction
1.1. The American Community Survey
The American Community Survey (ACS) is a part of the U.S. Census Bureau's Decennial Census Program and is designed to provide more current demographic, social, economic, and housing estimates throughout the decade. The ACS provides information on more than 40 topics, including education, language ability, the foreign-born, marital status, migration and many more. Each year the survey randomly samples around 3.5 million addresses and produces statistics that cover 1-year, 3-year, and 5-year periods for geographic areas in the United States and Puerto Rico. The 5-year estimates are available for many distinct geographies including the nation, all 50 states, DC, Puerto Rico, counties, places, census tracts, and block groups. For more information about the ACS, please visit our home page at: http://www.census.gov/acs. ACS tables are published on the Census Bureau's American FactFinder (AFF) website factfinder2.census.gov, and are available for download in several forms. This document will brief data users on the contents of the ACS Summary File and explain how they can use it to obtain the 5-year estimates.

1.2. The American Community Survey Summary File
The American Community Survey Summary File (ACSSF) is a unique data product that includes all the estimates and margins of error from the Detailed Tables and geographies that are published for the ACS. Other ACS data products such as Subject Tables and Data Profiles are created from the Detailed Tables and are therefore not available in the Summary File.
Since the Detailed Tables contain a large number of cells, the tables are stored in a series of files with only the data from the tables, without such information as the title of the tables, the description of the rows, and the names of the geographic areas. That information is in other files that the user must merge with the data files to reproduce the tables.
The ACS Summary File data files are in American Standard Code for Information Interchange (ASCII) format. The files are divided into three types:
  • Geographies - (position based and comma delimited)
  • Estimates - (comma delimited)
  • Margins of Error - (comma delimited)
Chapter 2 discusses each component in detail and explains how to put them all together.

1.3. Topics and Geographies Covered
Data contained in the ACS Summary File cover demographic, social, economic, and housing subject areas. All Detailed Tables for the ACS 5-year estimates are in the Summary File and are listed in Appendix E.

The published ACS Summary File geographies cover areas that are based on "summary levels". A summary level specifies the content and the hierarchical relationships of the geographic elements that are required to tabulate and summarize data. For example, summary level code "040" represents the U.S. States, Washington D.C., and Puerto Rico; while summary level code "050" represents counties and county equivalents within states.

The ACS 5-year estimates contain additional summary levels, such as census tracts and block groups, that are not published in the ACS 1-year and 3-year estimates. Visit Appendix F for the full list of summary levels published for the 5-year Detailed Tables. Estimates for census block groups are only available in the ACS Summary File; they are not published in American FactFinder. Visit Appendix F for the list of tables available at the block group level.

Many resources are available to help users understand the ACS geographic terms and concepts. For additional information, please visit www.census.gov/geo/www/reference.html and http://www.census.gov/acs/www/guidance_for_data_users/geography/. Users may also find the full list of summary levels published for the 5-year Detailed Tables in Appendix F.

1.4. Tools for Obtaining Data
Since using the ACS Summary File can be challenging, users should first check if their tables of interest are available for download on American FactFinder. Below are some other options to help users retrieve the tables they want. They are listed in order based on ease of use.
  • Summary File Excel Retrieval Tool
The Summary File Excel Retrieval Tool is a macro-driven Excel spreadsheet that provides a method to easily retrieve a table for the nation, states, and all of the geographic areas in a state (or for all cross-state geographic areas such as metropolitan statistical areas or census regions). This tool is designed to be easy to use, and does not require any programming experience. There is a drop down menu from which the user can select the state for the table and receive data for all geographies within the state. One key requirement is that Microsoft Excel 2007 or later is needed. Other hardware and software requirements for the tool are listed in Chapter 3.1. For more information about the application, visit the ACS Summary File page at http://www.census.gov/acs/www/data_documentation/summary_file/.
  • Summary File DataFerrett Tool
DataFerrett is a Census Bureau free online tool that can analyze and extract data from a variety of datasets, including the ACS Summary File. This tool is ideal for data users who wish to view, customize, and restrict the data that is downloaded from the ACS Summary File. Among the features provided by this tool is the ability to construct user-defined variables from the variables on the input data file(s), the ability for users to exclude data that is not of interest, a variety of options for downloading data, and the ability to create complex tabular reports from the data including graphs and thematic maps. The 20072011 ACS 5-year Summary File data in DataFerrett focuses primarily on the display and download capabilities of this tool. For example, users can download 74,100 geographic areas at one time. This means that all tracts for a table can be downloaded at once, and all block groups for a table can be downloaded in batches. This tool should be available for use a week after the 5-Year data release.
  • Summary File Excel Import Tool
The Summary File Excel Import Tool is a replicate of the Excel templates that Census 2000 provided for the SF3 summary file release. The Excel Import Tool provides a basic layout of each sequence in Excel in the same format as the estimate and margin of error files are formatted. For individuals that do not have Excel 2007 or later and are unable to use the Excel Retrieval Tool, the Excel Import Tool provides an alternative option to read the summary file into Excel. For more information on this tool, see Chapter 3.3.
  • SAS Programs
There are two programming options for SAS users. The first option is a set of individual SAS programs, one for each summary file by geography and sequence. These programs are best for users only interested in looking at a specific sequence for a specific geography. The second option is a single SAS program that is parameterized to allow users to read in any sequence for any geography into SAS. This program can also be used to read the entire summary file into SAS, and is designed for users looking for a large amount of data. For more information on these programs, see Chapter 3.1.

1.5. Notable Changes to the Summary File
For those who have used the ACS Summary File in previous years, the files for the 5-year estimates are similar to prior publications, with the following exceptions:

  • Table Sequencing Now Follows New Rules
In previous years, tables were sorted by subject. Tables are now sorted numerically by the "root" of their Table ID, where the "root" is defined as the numeric section after the first letter and before any additional letters, so for example the root of B06004APR is "06004." Learn more in Chapter 2.3 Sequence Numbers.
  • Geographic Area Name Length Increased
The field size of geographic variable "NAME" (area name) is now 1000 characters, increased from 200 characters in previous years. This change is documented in the layout of the geography file in Chapter 2.4 Geography File.

1.6. Contact Us
Please send any technical questions or comments on the ACS Summary File you have via email to: acso.users.support@census.gov. If you have questions or comments about the American Community Survey, you can submit a question online at ask.census.gov/.