<p>The American Community Survey (ACS) is a nationwide survey from the U.S. Census Bureau that replaces the decennial census “long form” survey. Like the decennial long form it replaces, the ACS gathers information from a subset of the U.S. population. However, the ACS is conducted on a continual, monthly basis. This enables estimates from the ACS to be published every year, giving a more current view of the characteristics of the population and housing.</p>
<p><strong>What Subjects Are Covered</strong></p>
<p>The ACS collects information on a wide range of characteristics from a sample of persons and households in the U.S.:</p>
<ul>
<li>Demographic (see a <a href="documents/Departments/OPCD/Demographics/AmericanCommunitySurvey/DemographicandHousingEstimates.pdf" target="">demographic sample</a>)
<ul style="list-style-type: disc;">
<li>Age</li>
<li>Sex</li>
<li>Race and ethnicity</li>
</ul>
</li>
<li>Social (see a <a href="documents/Departments/OPCD/Demographics/AmericanCommunitySurvey/SelectedSocialCharacteristics.pdf" target="">social sample</a>)
<ul style="list-style-type: disc;">
<li>Household composition and relationships</li>
<li>Marital status and fertility</li>
<li>School enrollment and educational attainment</li>
<li>Place of birth</li>
<li>Language spoken</li>
<li>Ancestry</li>
</ul>
</li>
<li>Economic (see an <a href="documents/Departments/OPCD/Demographics/AmericanCommunitySurvey/SelectedEconomicCharacteristics.pdf" target="">economic sample</a>)
<ul style="list-style-type: disc;">
<li>Employment status, industry, and occupation</li>
<li>Commuting to work</li>
<li>Incomes and benefits</li>
<li>Poverty</li>
</ul>
</li>
<li>Housing (see a <a href="documents/Departments/OPCD/Demographics/AmericanCommunitySurvey/SelectedHousingCharacteristics.pdf" target="">housing sample</a>)
<ul style="list-style-type: disc;">
<li>Occupancy and tenure (owner or renter occupancy)</li>
<li>Home value and monthly housing costs</li>
<li>Other housing characteristics such as size of structure and year built</li>
</ul>
</li>
</ul>
<p><strong>What Is Published</strong></p>
<p>ACS data are combined over different time periods and published by the U.S. Census Bureau annually in three series. Please see the various tabs for more information.</p>
<ul>
<li>1-year estimates
<ul style="list-style-type: disc;">
<li>Data collected over a 12-month period</li>
<li>Only for areas with populations of 65,000+</li>
<li>Smallest sample, less reliable, most current</li>
<li>Best used when recent estimates are more important than precise estimates and analyzing large populations</li>
</ul>
</li>
<li>3-year estimates
<ul style="list-style-type: disc;">
<li>Data collected over a 36-month period</li>
<li>Populations of 20,000+</li>
<li>Larger sample, more reliable, less current</li>
<li>Best used when analyzing smaller populations</li>
</ul>
</li>
<li>5-year estimates
<ul style="list-style-type: disc;">
<li>Data collected over a 60-month period</li>
<li>All geographic areas down to census tract or block group level — Note that the 5-year estimates are the only ACS estimates available at a neighborhood scale</li>
<li>Largest sample, most reliable, least current</li>
<li>Best used when accuracy is more important than having recent estimates and analyzing very small populations</li>
</ul>
</li>
</ul>
<p><strong>What You Need to Know</strong></p>
<p>There are some important ideas to keep in mind when using ACS data and products:</p>
<ul>
<li>Characteristics - ACS tells us about the <strong>characteristics</strong> of the population, not counts, because it is a done with a <strong>sample</strong> of the population.</li>
<li>Period Estimates - ACS estimates reflect the characteristics of the population and housing over the <strong>entire</strong> period of time the data were collected, not for any particular point in the period.</li>
<li>Margins of Error - ACS estimates carry margins of error which indicate how reliable the estimate is, with bigger margins of error signaling lower reliability.<br /><br />To use the ACS responsibly, pay attention to margins of error and make a careful decision about whether the reliability of the estimates is high enough for your purposes.
<ul style="list-style-type: disc;">
<li>Margins of error can be quite large, especially for small areas and population groups.</li>
<li>1-year estimates generally have much higher margins of error than the multi-year estimates.</li>
<li>Although more accurate, the 5-year estimates still tend to have higher margins of error than the decennial census long form estimates due to the lower sampling rates in the ACS</li>
</ul>
</li>
<li>Comparing Estimates - making comparisons using ACS data is complicated.
<ul style="list-style-type: disc;">
<li>Differences in estimates may not reflect actual differences, margins of error need to be considered.</li>
<li>Although the ACS and past decennial census long forms cover similar topics, estimates for some should only be compared with caution or not at all.</li>
</ul>
</li>
</ul>
<p><strong>What Else You Should Know</strong></p>
<p>For a more detailed discussion of the issues involved with using ACS data please see the ACS data issues tab at the top of this page.</p>