The American Community Survey (ACS) is a relatively new survey conducted by the U.S. Census Bureau. It uses a series of monthly samples to produce annually updated data for the same small areas (census tracts and block groups) formerly surveyed via the decennial census long-form sample. Initially, 5 years of samples will be required to produce these small-area data. Once the Census Bureau has collected 5 years of data, new small-area data will be produced annually. The Census Bureau also will produce 3-year and 1-year data products for larger geographic areas. The ACS includes people living in both housing units (HUs) and group quarters (GQs). The ACS is conducted throughout the United States and in Puerto Rico, where it is called the Puerto Rico Community Survey (PRCS). For ease of discussion, the term ACS is used here to represent both surveys. This document describes the basic ACS design and methodology as of the 2007 data collection year. The purpose of this document is to provide data users and other interested individuals with documentation of the methods used in the ACS. Future updates of this report are planned to reflect additional design and methodology changes. This document is organized into 15 chapters. Each chapter includes an Overview, followed by detailed documentation, and a list of references. Chapter 2 provides a short summary of the history and evolution of the ACS, including its origins, the development of a survey prototype, results from national testing, and its implementation procedures for the 2007 data collection year.
Chapters 3 and 4 focus on the ACS sample. Chapter 3 describes the survey frame, including methods for updating it. Chapter 4 documents the ACS sample design, including how samples are selected.
Chapters 5 and 6 describe the content covered by the ACS and define several of its critical basic concepts. Chapter 5 provides information on the surveys content development process and addresses the process for considering changes to existing content. Chapter 6 explains the interview and residence rules used in ACS data collection and includes definitions of key concepts covered in the survey.
Chapters 7, 8, and 9 cover data collection and data capture methods and procedures. Chapter 7 focuses on the methods used to collect data from respondents who live in HUs, while Chapter 8 focuses on methods used to interview those living in GQs. Chapter 9 discusses the ACS language assistance program, which serves as a critical support for data collection.
Chapters 10, 11, and 12 focus on ACS data processing, weighting and estimation, and variance estimation methods. Chapter 10 discusses data preparation activities, including the coding required to produce files for certain data processing activities. Chapter 11 is a technical discussion of the process used to produce survey weights, while Chapter 12 describes the methods used to produce variance estimates.
Chapters 13 and 14 cover the definition, production, and dissemination of ACS data products. Chapter 13 explains the process used to produce, review, and release ACS data. Chapter 14 explains how to access ACS data products and provides examples of each type of data product.
Chapter 15 documents the methods used in the ACS to control for nonsampling error, and includes examples of measures of quality produced annually to accompany each data release. A glossary of terms and acronyms used in this report appear at the end. Also, note that the first release of this report, issued May 2006, contained an extensive list of appendixes that included copies of forms and letters used in the data collection operations for the ACS. The size of these documents and the changing nature of some of them precludes their inclusion here. Readers are encouraged to review the ACS Web site www.census.gov
if data collection materials are needed or are of interest.