American Community Survey Product
↓ When to use 1-year, 3-year, or 5-year estimates
The ACS has all of the variables grouped into Tables and all of the Tables grouped into Categories. In order to make a selection to choose a Category and then either the entire table or some subset of it. The ACS has the following Category topics:
- Geography Fields
- Unweighted Count
- Hispanic Origin
- Foreign Birth
- Place of Birth - Native
- Residence Last Year - Migration
- Journey to Work
- Children - Relationship
- Grand(Persons) - Age of Household Members
- Households - Families
- Marital Status
- School Enrollment
- Educational Attainment
- Veteran Status
- Transfer Programs
- Employment Status
- Industry-Occupation-Class of Worker
- Group Quarters
- Health Insurance
- Computer and Internet Usage (only available on the 1-year estimates)
- Quality Measures
|1-Year Estimates||✪ 1552 variables|
|3-Year Estimates||✪ 1369 variables|
|5-Year Estimates||✪ 1009 variables|
2009 ACS 1-year estimates:
The US Census Bureau introduces new variables most years. When they are introduced and the data collected it will first become available in the 1-Year Estimates. For example if a new variable is introduced in 2014 it will be included in the 1-Year Estimates starting in 2014 but it will not be available in the 5-Year Estimates until 2018 (after 5 years of data collection).
The 1-Year Estimates are only available for those geographies with a population of at least 65,000. That means you can run states or MSAs but if you try to run Counties you will only get 831 of the 3,220 counties to appear. The others simply don’t meet the population threshold and are suppressed (the USCB’s decision not ours).
2007-2009 ACS 3-year estimates
ACS 3-Year Estimates was available on our 2009, 2010, 2011, 2012 and 2013 versions but have been dropped for the 2010-2014 and all later data releases.
The 3-Year Estimates are only available for those geographies with a population of at least 20,000. That means you can run states or MSAs but if you try to run Counties you will only get 1,909 of the 3,220 counties to appear. The others simply don’t meet the population threshold and are suppressed (the USCB’s decision not ours).
The 5-year ACS files were released by Geolytics for the first time in 2009 because that was when the data became available down to the block group and tract level.
The 5-Year ACS files are the replacement for the Long Form – giving us detailed information about the American population at small geographies, like Block Groups and Tracts
The ACS samples nearly 3 million addresses each year, resulting in nearly 2 million final interviews. The annual ACS sample is smaller than that of the Census 2000 Long Form sample, which included about 18 million housing units. As a result, the ACS needs to combine population or housing data from multiple years to produce reliable numbers for small counties, neighborhoods, and other local areas
Every year the US Census Bureau (USCB) will release a new single year ACS survey and replace the oldest year with this new data for the 1- and 5-year estimated numbers.
American Community Survey Geographies
ACS estimates use the legal boundaries as defined and available effective January 1st of the estimated year. For 3- and 5-Year estimates, the boundaries that are available and effective as of January 1 of the last year of the multiyear estimate period are used. So, for example, the 2005-2009 ACS 5-year estimates are based on boundaries as of January 1, 2009 which is the 2000 Census. Whereas the 2006-2010 ACS or any subsequent year will be based upon the new 2010 boundaries.
If you want the data in the 2000 boundaries – select the 2009 ACS. If you want the data in the 2010 boundaries than select the 2010 (or later) versions instead.
The ACS includes Data for the following geographies (the number in brackets indicates how many of each geography exist in the US including Puerto Rico):
- US (1)
- Region (4)
- Division (9)
- State (52 includes Puerto Rico and Washington DC)
- County (3,221)
- County Subdivisions (36,642)
- Place (29,514)
- Zip Code Tabulation Area (33,092) – starting with the 2011 ACS
- Census Tract (74,002)
- Block Group (220,334)
- Consolidated City (7)
- American Indian Area/Alaskan Native Area/Hawaiian Home Land (720)
- Alaska Native Regional Corporation (12)
- Metropolitan and Micropolitan Statistical Area (1,026)
- Combined Statistical Areas (163)
- Metropolitan Statistical Areas – Micropolitan Division (29)
- Metropolitan / Micropolitan Indicator Flag (29) – not mapable just data
- New England City and Town Areas (52)
- New England City and Town Combined Statistical Areas (17)
- New England City and Town Area Divisions (9)
- Urban Areas (3,607)
- Current Congressional District (437)
- State Legislative District Upper (1,976)
- State Legislative District Lower (4,786)
- State School District (Elementary) (2,328)
- State School District (Secondary) (533)
- State School District (Unified) (10,916)
- Urban/Rural (104) – not mapable just data
- Principal City Indicator (1,309) – not mapable just data
- Public Use Microdata 5% file (2,101)
When to use 1-year, 3-year, or 5-year estimates
Choosing which dataset involves more than simply considering the population size in your area. You must think about the balance between currency and sample size/reliability/precision.
For details, research implications, and examples, see "Understanding and Using ACS Single-Year and Multiyear Estimates," page 9 in General Data Users Handbook
Distinguishing features of ACS 1-year, 3-year, and 5-year estimates
|1-year estimates||3-year estimates||5-year estimates|
|12 months of collected data||36 months of collected data||60 months of collected data|
|Data for areas with populations of 65,000+||Data for areas with populations of 20,000+||Data for all areas|
|Smallest sample size||Larger sample size than 1-year||Largest sample size|
|Less reliable than 3-year or 5-year||More reliable than 1-year; less reliable than 5-year||Most reliable|
|Most current data||Less current than 1-year estimates; more current than 5-year||Least current|
|Best used when||Best used when||Best used when|
|Currency is more important than precision
Analyzing large populations
|More precise than 1-year, more current than 5-year
Analyzing smaller populations
Examining smaller geographies because 1-year estimates are not available
|Precision is more important than currency
Analyzing very small populations
Examining tracts and other smaller geographies because 1-year estimates are not available
General Guidance for comparing ACS multiyear estimates
- If you want to compare estimates for different areas, use the same ACS data file – you should not compare a 1-year estimate for one area to a 3-year estimate for another area.
- The Census Bureau discourages direct comparisons between estimates for overlapping periods. Instead, compare non-overlapping estimates. Thus you should not compare the 2005-2007 ACS estimates to the 2006-2008 ACS estimates. It is better to compare 2005-2007 ACS to the 2008-2010 ACS estimate.
- The power of the ACS is in estimating demographic distributions. So users are encouraged to analyze derived measures such as percents, means, medians, and rates rather than estimates of population totals.
For additional guidance in comparing ACS estimates to Census 2000 data the US Census Bureau offers the following tools: for an overview, use the quick guide, to compare by subject browse the subject/topic comparison chart, or use the table comparison tool to search by table number.
For more information you may want to read through the Handbooks that the Census Bureau publishes – they are found on the Census website at: