American Community Survey (ACS)

The Census Bureau encourages users to compare ACS data with data from Census 2000 and previous ACS releases. Guidance is needed before drawing conclusions because in some instances comparisons could be misleading due to differences in questions or methods. This page provides three forms of guidance - general guidance, item-specific guidance, and examples. For all comparisons of differing time periods, users should take into consideration that geographic boundaries for the area of interest may have changed.

General Guidance

Our general guidance for comparing 2007 ACS data with data from the 2006 ACS and with Census 2000 is provided below.

Although the ACS produces population, demographic and housing estimates, it is the Census Bureau's Population Estimates Program that produces and disseminates the official estimates of the population for the nation, states, counties, cities and towns and estimates of housing units for states and counties. The ACS should be used to examine housing, demographic, social, and economic characteristics of the population.

Comparing 2007 ACS Data to 2006 ACS Data - The Census Bureau supports comparisons made between 2006 and 2007 ACS data, however, substantial changes in the ACS GQ estimates can impact ACS estimates of total population characteristics. This is especially true for areas where either the GQ population is a substantial proportion of the total population or where the GQ population may have very different characteristics than the total population as a whole.

Beginning this year a new data product for 1-year estimates, the comparison profiles, will be available for geographic areas with a population of 65,000 or more. The comparison profiles display the percent distribution of 2007 and 2006 ACS data for selected demographic, social, economic, and housing characteristics. They also display estimates of ratio and medians for a small number of characteristics. In addition, differences that are statistically significant at the 90 percent confidence level are indicated by an '*'. For more information, please see the Quick Guide. However, in some instances, caution should be used in making comparisons. See Item-Specific Guidance for more details.

Comparing 2007 ACS Data to Census 2000 Data - There are global differences that exist between the 2007 ACS and Census 2000. These include differences in residence rules, universes, and reference periods. For example, the 2007 ACS uses a "two-month" residence rule - defined as anyone living for more than two months in the sample unit when the unit is interviewed whereas Census 2000 used a "usual residence" rule - defined as the place where a person lives or stays most of the time.

The Census Bureau subject matter specialists have reviewed all of these factors and have determined that for most population and housing subjects, comparisons can be made.

Item-Specific Guidance

Specific item-level guidance is provided in the table below. This table identifies all items included in the ACS. Scroll down the first column to find the item of interest. Specific guidance is given for each item on comparing 2007 ACS data with data from Census 2000 and with data from the 2006 ACS. Selecting "more info" links you to a detailed explanation of why we recommend to "Compare with Caution" or "Do Not Compare" the data. Generally, when it is recommended to "Compare" the data, no additional information is provided. However, in cases where additional information is needed, it is provided. Selecting "table crosswalk" links you to information that identifies the 2006 ACS detailed tables for a specific item and the corresponding tables in the Census 2000 Summary File (SF 3) for that item. In most cases, the 2007 and 2006 ACS detailed tables are structured exactly the same as the SF 3 table. However, there are some instances in which the ACS tables show more detail or show less detail than the SF 3 table.

Because the 2007 ACS detailed tables do not largely differ from the 2006 ACS detailed tables, the "table crosswalk," which compares 2006 ACS detailed tables to SF 3 tables, was not updated. Therefore, to determine if a 2007 ACS detailed table is directly comparable to a SF3 table, the 2006 "table crosswalk" should be used.

For a complete list of changes between the 2007 ACS and the 2006 ACS detailed tables, please see "list of changes between 2006 and 2007 detailed tables" (Excel file.)

For guidance on comparing 2006 ACS to other data source, go to Guidance on Comparing 2006 ACS Data to Other Sources

Examples

"Examples" are provided to demonstrate how one would navigate through the web site to get guidance on a particular item of interest.

* Each subject area is listed with its 2-digit code. This code corresponds to the second and third characters of the ACS table number. For example, Table B08303 - Travel Time to Work - has the digits of "08" in the second and third position. This corresponds to the subject Journey to Work; Workers; and Commuting.
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