Introducing a new way to navigate by topics. Access the latest news, data, publications and more around topics of interest.
Our population statistics cover age, sex, race, Hispanic origin, migration, ancestry, language use, veterans, as well as population estimates and projections.
This section provides information on a range of educational topics, from educational attainment and school enrollment to school districts, costs and financing.
We measure the state of the nations workforce, including employment and unemployment levels, weeks and hours worked, occupations, and commuting.
Our statistics highlight trends in household and family composition, describe characteristics of the residents of housing units, and show how they are related.
Health statistics on insurance coverage, disability, fertility and other health issues are increasingly important in measuring the nation's overall well-being.
We measure the housing and construction industry, track homeownership rates, and produce statistics on the physical and financial characteristics of our homes.
The U.S. Census Bureau is the official source for U.S. export and import statistics and regulations governing the reporting of exports from the U.S.
The U.S. Census Bureau provides data for the Federal, state and local governments as well as voting, redistricting, apportionment and congressional affairs.
Search an alphabetical index of keywords and phrases to access Census Bureau statistics, publications, products, services, data, and data tools.
Geography provides the framework for Census Bureau survey design, sample selection, data collection, tabulation, and dissemination.
Geography is central to the work of the Bureau, providing the framework for survey design, sample selection, data collection, tabulation, and dissemination.
Find resources on how to use geographic data and products with statistical data, educational blog postings, and presentations.
The Geographic Support System Initiative will integrate improved address coverage, spatial feature updates, and enhanced quality assessment and measurement.
Work with interactive mapping tools from across the Census Bureau.
Find geographic data and products such as Shapefiles, KMLs, TIGERweb, boundary files, geographic relationship files, and reference and thematic maps.
Metropolitan and micropolitan areas are geographic entities used by Federal statistical agencies in collecting, tabulating, and publishing Federal statistics.
Find information about specific partnership programs and learn more about our partnerships with other organizations.
Definitions of geographic terms, why geographic areas are defined, and how the Census Bureau defines geographic areas.
We conduct research on geographic topics such as how to define geographic areas and how geography changes over time.
Visit our library of Census Bureau multimedia files. Collection formats include audio, video, mobile apps, images, and publications.
Collection of audio features and sound bites.
The Census Bureau packages data and information into easy-to-understand visuals.
Browse Census Bureau images.
Read briefs and reports from Census Bureau experts.
Watch Census Bureau vignettes, testimonials, and video files.
Read research analyses from Census Bureau experts.
Access data through products and tools including data visualizations, mobile apps, interactive web apps and other software.
Developer portal to access services and documentation for the Census Bureau's APIs.
Explore Census Bureau data on your mobile device with interactive tools.
Find a multitude of DVDs, CDs and publications in print by topic.
These external sites provide more data.
Download extraction tools to help you get the in-depth data you need.
Learn more about our data from this collection of e-tutorials, presentations, webinars and other training materials. Sign up for training sessions.
Explore Census data with interactive visualizations covering a broad range of topics.
Learn how we serve the public as the most reliable source of data about the nation's people and economy.
How we provide the best mix of timeliness, relevancy, quality, and cost for the data we collect.
Our researchers explore innovative ways to conduct surveys, increase respondent participation, reduce costs, and improve accuracy.
Our surveys provide periodic and comprehensive statistics about the nation, critical for government programs, policies, and decisionmaking.
Learn about other opportunities to collaborate with us.
Explore the rich historical background of an organization with roots almost as old as the nation.
Explore prospective positions available at the Census Bureau.
Explore Census programs targeted for particular needs.
Discover the latest in Census Bureau data releases, reports, and events.
The Census Bureau's Director writes on how we measure America's people, places and economy.
Find interesting and quirky statistics regarding national celebrations and major events.
Listen to audio files on fun facts, historical figures, and celebrations of the month.
Find media toolkits, advisories, and all the latest Census news.
See what's coming up in releases and reports.
1. How large is the sample?
The full implementation of the ACS, which began in 2005, sampled approximately 2.9 million housing unit addresses annually stateside. The PRCS sampled approximately 36,000 housing unit addresses each year in Puerto Rico. The 2011 ACS sampled approximately 3.3 million housing unit addresses - this corresponds to an increase in the targeted annual sample size of 3.54 million addresses that began with the June 2011 ACS sample. This increase in the targeted annual sample size has continued since then, resulting in a 2013 ACS sample of approximately 3.54 million housing unit addresses.
The full implementation of the ACS and PRCS Group Quarters data collection began in 2006. There are approximately 200,000 persons in the group quarters sample each calendar year in the ACS.
The ACS sampled between 740,000 and 900,000 housing unit addresses annually in 2000 through 2004.
2. What is sampling error?
The ACS estimates are based on data from a sample of housing units and people in the population, not the full population. For this reason, ACS estimates have a degree of uncertainty associated with them, called sampling error. In general, the larger the sample, the smaller the level of sampling error.
3. Why is it important to measure sampling error?
The estimates produced by the ACS are not exact because they are based on a sample. The sampling error measures the degree of uncertainty associated with the estimates. If the degree of uncertainty is too large, then users should be cautious in how the estimates are used.
4. How does the ACS measure sampling error
The ACS calculates standard errors for each estimate produced and publishes the 90 percent confidence level margins of error (the Census Bureau standard). You can be 90 percent confident that the interval within the margin of error from the estimate includes the true value. See Accuracy of the Data for more details on how margins of error and confidence intervals are calculated and interpreted.
5. What other numbers provide important information on the reliability of ACS estimates?
Housing Units Initial Addresses Selected - The number of addresses in each state and for the nation that were selected for the ACS sample for a particular year. Each year's sample is systematically divided into 12 monthly samples for ACS interviewing. This initial number includes addresses later determined to be commercial or nonexistent, as well as housing units that are not interviewed due to subsampling for personal visit follow-up, refusals, or other reasons.
Housing Units Final Interviews - The final number of interviews across all three modes of data collection for the ACS in a given year for the nation and by state. This number includes occupied and vacant housing units that were interviewed by the internet, mail, telephone, or personal visit methods between January 1 - December 31. It excludes addresses determined to be nonexistent or commercial, and addresses not selected in the subsample for personal visit follow-up, and addresses that are not interviewed due to refusals or other reasons.
Group Quarters People Initial Sample Selected - The number of people living in GQs that could be contacted for ACS interviewing in a given year for the nation and by state. Each year's sample is systematically divided into 12 monthly samples for ACS interviewing. This initial number includes people thought to be in group quarters that were later determined to be out of scope or nonexistent, as well as people not interviewed due to the group quarter refusing entry, the person refusing to respond, or other reasons.
Group Quarters People Actual Final Interviews - The final number of actual person interviews for the ACS for those living in group quarters in a given year for the nation and by state.
Group Quarters People Synthetic Final Interviews - The final number of synthetic person interviews for the ACS in a given year, for the nation and by state. For more information, see the User Note on synthetic interviews.
6. Are these numbers used to calculate the survey response rate?
These numbers by themselves are not used to measure the response to the request to participate in the ACS. See Survey Response Rates - Definitions for more information.
7. How does the ACS calculate these five measures of sample size?
|Housing Units Initial Addresses Selected (state x, year y) =||the sum of the twelve monthly housing unit address samples selected from the Master Address File for state x in year y.|
|Housing Units Final Interviews (state x, year y) =||the sum of all housing unit interviews successfully conducted by internet, mail, telephone, or personal visit between January 1 and December 31 of year y, in state x|
|Group Quarters Initial Sample Selected (state x, year y) =||the sum of expected sample persons across sample GQs in state x, year y.|
|Group Quarters Actual Final Interviews (state x, year y) =||the sum of all actual interviews between January 1 and December 31 of year y, for state x.|
|Group Quarters Synthetic Final Interviews (state x, year y) =||the sum of all synthetic interviews between January 1 and December 31 of year y, in state x.|