Important Features and Limitations of the Current Release of the ACS 5-Year Summary File in DataFerrett

December 2011

I.  Introduction

1. What is available? The ACS 5-Year Summary File data for both the 2005-2009 and 2006-2010 periods are available for users to define subsets of the data to download and to produce reports using the data.
2. What should I do before accessing this dataset in DataFerrett? It is recommended that each user go through the Supplement to the User Guide for the ACS Summary File before accessing the ACS Summary File in DataFerrett.
3. How do I access the ACS Summary File data in DataFerrett? You can access DataFerrett by going to http://dataferrett.census.gov/run.html
4. Recommended web browsers and PC configuration
   1. PCs: Internet Explorer, Mozilla/Firefox, Google Chrome
   2. Macs: Safari, Internet Explorer, Mozilla/Firefox
   3. In order for DataFerrett to tabulate and map a large number of geographic areas the JAVA applet memory size may need to be increased. To do this on a PC:
   1. Open the control panel from the Start menu
   2. Double-click on the JAVA icon
   3. Click on the JAVA tab in the window that opens
   4. Click on the View button in the "Java Applet Runtime Settings" section.
   5. Double click in the cell under "Runtime Parameters" and type in the following:
      
      -Xmx512m.
      
      NOTE: If there are two cells in the "Runtime Parameters" column, enter the text into both cells.
   6. Click on the OK button
   7. Click on the Apply button
5. Differences between the data extracted from DataFerrett and the data downloaded from the Census Bureau FTP site

   The DataFerrett approach is more similar to American FactFinder (AFF). In DataFerrett and AFF, the user selects tables from a list and views or downloads the selected data. When using the ACS Summary Files from the Census Bureau FTP site, on the other hand, users need to draw on information from several separate files (e.g., the "sequence number" file, the geography file, etc.).

II.  Important Features and Limitations of the DataFerrett Release on January 31, 2011

1. All 930 detailed tables in the ACS Summary File are included
2. All tables released at the census block group level are included
3. Each extract will be run non-interactively (i.e., in "batch" mode), and the user will be notified by email when the data is ready to be downloaded to the user's computer. There is no limit to the number of extracts that a user can submit.
4. The label for a data cell in a table may include "!!". This is a delimiter between the parts of the label representing the different levels of the hierarchy that include this data cell.
5. Many geographic summary levels are not included; they will be included in a later release. See the table below for a list of the geographic summary levels included in the initial release.
6. This application is not meant for the user who wants to download the entire ACS summary file. Users will be able to extract and download small or large subsets of the Summary File data, but there are size limits for a single extract: NOTE: the word "variable" in DataFerrett refers to any data item the user can view and add to her/his "data basket". This includes data cells and margins of error of the tables as well as geographic data items.
7. Limitations on DataFerrett extracts and data downloads:
   • No more than 74,100 geographic areas, and, if the maximum number of geographic areas is used, then no more than 200 variables may be included in the extract.
   • Extracts greater than 10 megabytes in size must be downloaded as compressed files (i.e., in a "zip" format).
   • No extract can contain more than 14,820,000 cells (the product of 200 variables and 74,100 geographic areas).
   • No more than 535 variables in any single extract - this is a change from earlier versions, but the number does not include margins of error. This means that, as long as none of the other limits are exceeded, a user can request up to about 530 estimates in an extract. It is important to include the geographic variables when calculating an extract with 400 estimates from different detailed tables for all counties in the U.S. since this would be well below the limit of 14,820,000 cells.
8. A user may now include data cells from more than four detailed tables in a single extract request; i.e., there is no longer a limitation of four tables per extract request.
9. Since the initial release, the "Make a Table" path (including mapping) has been much more thoroughly tested and many problems found have been corrected.

10. Thematic mapping is available for several geographic summary levels: see table 1 below.
    NOTE: User must know before selecting geography for a detailed table if the table is available at this geographic level. Otherwise, DataFerrett will return "null" values for the table. (For detailed information about the geographic areas for which a detailed table is available, see Appendix E of the ACS Summary File Tech Doc.)

11. New! Margins of Error (MOEs) are now treated as attibutes of the estimates. This means they are no longer selectable as independent variables. The user can now choose to include or exclude the margins of error in an extract. If they are to be included, they can be output in a separate file or interleaved with the estimates in a single extract file. This new approach to the treatment of margins of error also affects their display and what can be done with the MOEs in the Make-a-Table window of DataFerrett. See the revised Supplement to the User Guide for the ACS Summary File for detailed information on these changes.

III.  Known Bugs

1. Currently, the Search feature in the "Step 1" screen does not work correctly under the following circumstances:
   

   If a user adds a variable found ONLY in 2006-2010 to the data basket and then attempts to search for another word or phrase, the search returns no results even if the 2006-2010 folder is highlighted. However, the search will work correctly in this case when the sub-folder named "5-Year Summary File" is highlighted.

2. This bug occurs when a user does the following sequence of steps:
   • Highlight the top-level folder under name "American Community Survey" in the list of data sets on the left hand side of the Step 1 window
   • Search for a term or phrase
   • From the list of "hits" returned by the search, choose a variable with "2005-2009-current" in the "Availability" column and add this variable to the data basket
   • Attempt to select geography in the "Ferrett Geography Codebook"; an empty list is displayed
   This is happening because the user has ot yet selected the 2005-2009 or the 2006-2010 Summary File data. To avoid this bug, highlight the folder naming the instance you want to use; i.e., "2006-2010" or "2005-2009" Summary File before executing the search. Then, proceed with selecting geography.
3. THIS BUG IS NOW FIXED: If a user attempts to create a thematic map for a non-mappable geography, the error message displayed is empty and therefore, of no use to the user.
4. THIS BUG IS NOW FIXED: The new feature allowing interleaving the margins of error with the estimates in the data extract does not work for the "space delimited" file type.
5. If a Ferrett Session File (FSF) or Ferrett Tabulation File (FTF) to be used with the 2005-2009 ACS Summary File data already exists, and you open this FSF/FTF in DataFerrett, you may encounter an error if you create a table in the Tabulation Window and attempt to create a thematic map for a data column of the table. Until this bug is fixed, a work-around would be to delete the geography variable for the geographic areas in column C1 of the table and then recreate it. Once you have done that, you should be able to recreate the table and create the desired thematic map.
6. THIS BUG IS NOW FIXED: There are problems that can occur in a table (in "Make a Table") when the SORT feature is used in conjunction with the feature allowing the user to show every data column as a percent of the first data column (the leftmost "%" icon). The percent data can become associated with the incorrect state.
7. THIS BUG IS NOW FIXED: The user should be able to use the View/Modifyaction in Step 2 to delete one of the geographic areas for a geographic variable added to the data basket in Step 1. However, when a user attempts this, the geographic area disappears from the list as expected, but it is not actually deleted. The geographic area will still be present in a data extract or in a table the user creates using this geography variable.
8. THIS BUG IS NOW FIXED: If a user specifies an extract in SAS file format, the generated SAS code may contain an error in a SAS format statement "the same value is equated with two or more different labels". This error does not always occur, but the user should be aware of it.
9. THIS BUG IS NOW FIXED: Geography Selection Wizard "if the user selects geographic areas from geographic "hierarchy" (e.g., state-county-tract) by selecting the higher level geography followed by a lower level geography before hitting the "Finish" button, the selections for the higher level geography will not be retained. To work around this error, the user should select geographic areas in a "hierarchy" from lowest level to highest level. For example, if the user wants all the counties in a state and all the tracts in the same state, the user should select the tracts first followed by the counties.

IV Geography

Refer to "Table 1: Geographic Summary Levels" of the Supplement to the User Guide for the ACS Summary File for a list of the types of geography for which the detailed tables are available in DataFerrett.