GEOG 160
Mapping Our Changing World

5. American Community Survey

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Beginning in 2010, the American Community Survey (ACS) replaced the "long form" that was used to collect sample data in past decennial censuses. Instead of sampling one in six households every ten years (about 18 million households in 2000), the ACS samples 2-3 million households every year. The goal of the ACS is to enable Census Bureau statisticians to produce more timely estimates of the demographic, economic, social, housing, and financial characteristics of the U.S. population. You can view a sample ACS questionnaire by entering the keywords "American Community Survey questionnaire" into your favorite Internet search engine.

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Acquiring and Understanding American Community Survey (ACS) Data

The purpose of this practice activity is to guide your exploration of ACS data and methodology. In the end you should be able to identify the types of geographical areas for which ACS data are available; to explain why 1-year and 3-year estimates are available for some areas and not for others; and to describe how the statistical reliability of ACS estimates vary among 1-year, 3-year and 5-year estimates. 

  1. Return to the U.S. Census Bureau site at http://www.census.gov.
  2. With your mouse cursor, hover over the People tab and under Related Content follow the link to American Community Survey. This takes you to the main American Community Survey page. (You can also find a link to American Community Survey by following the Subjects A to Z link in the upper right.)
  3. Begin by clicking the Guidance for Data Users tab and looking through the information available there.
    Pay particular attention to the When to use… section and the descriptions of the various estimates (1-, 3- and 5-year).  
    You will also find a section on Comparing ACS Data to other census data, a section on Handbooks for Data Users, and an E-Tutorial. (Some of the tutorial is not up to date relative to the new web pages, but you might benefit form Lesson3: Understanding the American Community Survey.)
  4. Next, look at the content under the Data & Documentation tab.
    In the Data section you will find release dates for the various datasets.
    In the Documentation section there are links to documentation associated with current and past surveys, and, under Accuracy of the Data, links to documents describing the methodology used and the accuracy of the data estimates.
    You can download ACS data to make maps and analyses using your own GIS or statistical software. Find download links and pertinent information in the sections titled Downloadable Data via FTP, and Summary File is information regarding downloading the data.
    There is also a section pertaining to Public Use Microdata Sample (PUMS). PUMS data are edited, however, to protect the confidentiality of individuals and households.
  5. In the remaining steps you will make a map or two, to reinforce the geographies covered by the ACS. You will map data from your home (or adopted) state.
    You need to go to the American FactFinder. If you are still at on the American Community Survey page, click the Data & Documentation tab, then follow the link to the American FactFinder website. You should land on the SEARCH page with American Community Survey in the Your Selections window, and a list of Search Results that are ACS-based.
    (If you were not already on the American Community Survey page, go to the MAIN American FactFinder site (http://factfinder2.census.gov), click the Topics search box, then expand the Program list and choose American Community Survey. Close the Select Topics overlay window.)
  6. Click the Geographies search options box (on the left) to reveal the Select Geographies overlay window. Under Geography Filter Options click County.  In the Geography Results area, check the box for All Counties within <your state>. The click Add. This will add the All Counties… entry to the Your Selections list. Close the Select Geographies overlay window.
    The Search Results window is apt to be showing a list of datasets for 2005. If you advance the page, the list will refresh so that page 1 shows datasets for 2010. Do so, in order to be viewing the list of 2010 datasets.
  7. In the Search Results window note that there are many datasets that have 1-, 3- and 5-year estimates entries. Decide upon a 1-Year dataset to look at and check the box for it. Then click View. On the new Results page that you land on be sure that the Create a Map choice is blue – not grayed out. If it is grayed out click the BACK TO SEARH button and make sure only one dataset box is checked, or make a different choice, then click View again.
    Click on Create a Map. The data values in the table will turn blue and you will be prompted to “Click on a data value in the table.” Clicking a single data value from any row will allow you to map the data in that row for all of the counties for which it is available. Click on a blue data value of your choice – remember which row you choose. Click on the SHOW MAP button in the small popup window that appears.
    Are all of the counties in the state symbolized as having data? Why not?
  8. Now click the BACK TO SEARCH button (in the upper left). Un-check the box for the 1-year dataset and check the box for the 3-year estimate of the same category. Proceed as above to map the data. After the map is refreshed note how many counties now exhibit data.
    Take a look at the 5-year estimates for the same dataset if you wish.
Practice Quiz Registered Penn State students should return now to the Chapter 3 folder  in ANGEL (via the Resources menu to the left) to take a self-assessment quiz about Census Attribute Data. You may take practice quizzes as many times as you wish. They are not scored and do not affect your grade in any way.