Sample data product names:

• 2009 American Community Survey 1-Year Estimates
• 2007-2009 American Community Survey 3-Year Estimates
• 2005-2009 American Community Survey 5-Year Estimates

Source: U.S. Census Bureau. A Compass for Understanding and Using American Community Survey Data: What Researchers Need to Know. May 2009, p. 8.
Data are released in the year following completion of data collection.

How to choose an American Community Survey data product

1. Decide which year you want data for.

2. Decide for what geographical area(s) you want to collect data.

3. Find out what the population of that geographical area is.

4. Determine which ACS data products are available for that year for a geographical area having that population.

5. Compare the data products (if there is more than one).

Example 1: geographical area with small population

1. Year: most current available

2. Geographical area: Roxana, Illinois

3. Population of Roxana, Illinois: 1,575 (2005-2009 American Community Survey 5-Year Estimates)

4. Available ACS data products:

   1. 2005-2009 American Community Survey 5-Year Estimates

5. For areas below 20,000 people, there is currently only one choice of ACS data product.

Example 2: geographical area with mid-size population

1. Year: most current available

2. Geographical area: Edwardsville, Illinois

3. Population of Edwardsville, Illinois: 24,030 (2005-2009 American Community Survey 5-Year Estimates)

4. Available ACS data products:

   1. 2005-2007 American Community Survey 3-Year Estimates*

   2. 2006-2008 American Community Survey 3-Year Estimates*

   3. 2007-2009 American Community Survey 3-Year Estimates

   4. 2005-2009 American Community Survey 5-Year Estimates

5. Comparison of available data products:

   1. c. 2007-2009 American Community Survey 3-Year Estimates: less reliable, more current

   2. d. 2005-2009 American Community Survey 5-Year Estimates: more reliable, less current

* Excluded because it is less current than another data product.

Example 3: geographical area with large population

1. Year: most current available

2. Geographical area: Madison County, Illinois

3. Population of Madison County, Illinois: 266,866 (2005-2009 American Community Survey 5-Year Estimates)

4. Available ACS data products:

   1. 2005 American Community Survey 1-Year Estimates*

   2. 2006 American Community Survey 1-Year Estimates*

   3. 2007 American Community Survey 1-Year Estimates*

   4. 2008 American Community Survey 1-Year Estimates*

   5. 2009 American Community Survey 1-Year Estimates

   6. 2005-2007 American Community Survey 3-Year Estimates*

   7. 2006-2008 American Community Survey 3-Year Estimates*

   8. 2007-2009 American Community Survey 3-Year Estimates

   9. 2005-2009 American Community Survey 5-Year Estimates

5. Comparison of available data products:

   1. e. 2009 American Community Survey 1-Year Estimates: least reliable, most current

   2. h. 2007-2009 American Community Survey 3-Year Estimates: less reliable, less current

   3. i. 2005-2009 American Community Survey 5-Year Estimates: most reliable, least current

* Excluded because it is less current than another data product.

Example 4: comparison of geographical areas

1. Year: most current available

2. Geographical area: compare Edwardsville, Illinois and Madison County, Illinois

3. Population of

   • Edwardsville, Illinois: 24,030 (2005-2009 American Community Survey 5-Year Estimates)

   • Madison County, Illinois: 266,866 (2005-2009 American Community Survey 5-Year Estimates)

4. Available ACS data products:

   • 3- and 5-year estimates are available for both Edwardsville and Madison County.

   • 1-year estimates are available for Madison County only.

5. Recommendation:

   • "The Census Bureau encourages comparing estimates based only on the same survey year(s)." (A Compass for Understanding and Using American Community Survey Data: What General Data Users Need to Know, p. 9. Page 10 of that publication includes discussion of other alternative techniques for comparing geographical areas.)

   • Thus, one would choose the same data product, either the 3- or the 5-year estimates, for both Edwardsville and Madison County.

Example 5: trend for smaller geographical area

1. Year: trend

2. Geographical area: Edwardsville, Illinois

3. Population of Edwardsville, Illinois: 24,030 (2005-2009 American Community Survey 5-Year Estimates)

4. Available ACS data products:

   1. 2005-2007 American Community Survey 3-Year Estimates

   2. 2006-2008 American Community Survey 3-Year Estimates

   3. 2007-2009 American Community Survey 3-Year Estimates

   4. 2005-2009 American Community Survey 5-Year Estimates

5. Recommendation:

   • "The Census Bureau suggests comparing periods that do not overlap—comparing 2005–2007 estimates with
     2008–2010 estimates [which have not yet been released-BL], for example." This is because comparing e.g. 2005-2007 and 2006-2008 3-year estimates may not show much difference, since 2 of the 3 years worth of data in the two data products are the same. (A Compass for Understanding and Using American Community Survey Data: What General Data Users Need to Know, p. 10.)

   • Fast and substantial changes may be visible in data products whose periods are fairly close in time. To see slower and smaller changes may require comparing data products whose periods are farther apart in time.

6. ! Hint: On American FactFinder, after choosing one of the more recent ACS 1-year estimates data products, the "Comparison Profiles" compare 1-year estimates for statistical significance.

When to use

CV: Coefficient of Variation
Source: A Compass for Understanding and Using American Community Survey Data: What General Data Users Need to Know, p. A-7.

For more information

• When to use 1-year, 3-year, or 5-year estimates

• A Compass for Understanding and Using American Community Survey Data: What General Data Users Need to Know, pp. 9-10, Appendix 1: Understanding and Using ACS Single-Year and Multiyear Estimates, and Appendix 4: Making Comparisons.