This handbook is intended to aid analysts, program administrators, and policy makers within federal agencies when they use the ACS in carrying out the business of their agencies. Because agencies depend on the detailed housing and socioeconomic data that have been provided by the decennial census longform sample, the advent of the ACS is of great interest and possibly some concern to the analysts and policy makers in agencies that use these data. Data users will want to know:

• Whether the ACS will provide the same information as the long form.

• Whether ACS data will be as reliable as long-form data.

• How having annual data will affect their programs.

• How program recipients might view the shift from the long-form census sample to the ACS.

This handbook is designed to help users in federal agencies understand the ACS and answer these questions. While this handbook will describe the essential features of the ACS in detail and will discuss some important statistical and practical considerations, the bottom line is that federal agencies should be able to use ACS data for the same purposes for which they used decennial census sample data. Clearly, the more frequent updating of information available in the ACS changes the statistical framework in which federal agencies have been operating and opens new opportunities for agencies to advance their missions and base policy