Important Features and Limitations of the Current Release of the 2005-2009 ACS 5-Year Summary File in DataFerrett

November 14, 2011 (released to beta in October 2011)

NOTE: This document replaces the earlier document issued on May 2011. In section II below, any changes to the list of features and limitations from the original document are highlighted in bold font.

I.  Introduction

1.     What is available? The 2005-2009 ACS 5-year Summary File data is 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 and the Hands-on Tutorial for the ACS Summary File

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

a.     PCs: Internet Explorer, Mozilla/Firefox, Google Chrome

b.     Macs: Safari, Internet Explorer, Mozilla/Firefox

c.     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:

                                      i.        Open the control panel from the Start menu

                                     ii.        Double-click on the JAVA icon

                                    iii.        Click on the JAVA tab in the window that opens

                                    iv.        Click on the View button in the "Java Applet Runtime Settings" section.

                                     v.        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.

                                    vi.        Click on the OK button

                                   vii.        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

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 67,000 geographic areas with up to 250 variables in the extract

·         Extracts greater than 10 megabytes in size must be downloaded as compressed files (i.e., in a "zip" format)

·         No more than 270 variables in any single extract - this is a change from earlier versions, but the number does not include margins of error (see item 11 below).

8.     New! 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; i.e., there is no longer a limitation of four tables per extract request.

9.     New! 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.) A small number of counties and county equivalents may not be correctly included in thematic maps the user can create at the county level in the "Make a Table" feature of Step 2 in DataFerrett. See the Geography Notes for 5-Year Release for details on these areas. These notes also provide detailed inforation on 26 counties in which the tracts and block groups used for the ACS Summary File were those defined for the 2010 Census instead of the Census 2000 definitions which are used for all other counties for the dataset.

11.   New! The margins of error (MOEs) are now treated as attributes of the estimates. This means that 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 (list below only includes those bugs relevant to the ACS Summary File dataset)

1.     Currently, the Search feature in the "Step 1" screen may not return all the matching results. In some instances, it may fail to find any of the matches.

2.     If a user attempts to create thematic map for a non-mappable geography the error message displayed is empty, and, therefore, of no use to the user.

3.     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.

4.     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.

5.     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.

6.     THIS BUG IS NOW FIXED! The user should be able to use the View/Modify action 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.

7.     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.

8.     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.

Table 1. Geographic Summary Levels in this release

Geographic
Summary
Level

Description

Thematic
Mapping
available?

Components
(see Appendix F of the
ACS Summary File Tech Doc
for details)

10

United States

No

All

20

Regions

No

All

30

Divisions

No

All

40

States

Yes (within U.S.)

All

50

Counties

Yes (within state and U.S.)

No

60

County Subdivisions

Yes (within county and state)

No

140

Census Tracts

Yes (within county and state)

No

150

Census Block Groups

Yes (within tract and county)

No

160

Places

Yes (within state)

No

250

American Indian Area/Alaska Native Area/Hawaiian Home Land

Yes (within U.S.)

No

310

Metropolitan Statistical Area/Micropolitan Statistical Area

Yes (within U.S.)

No

311

Metropolitan Statistical Area/Micropolitan Statistical Area-State

Yes (within state and U.S.)

No

330

Combined Statistical Area

Yes (within U.S.)

No

331

Combined Statistical Area-State

Yes (within state and U.S.)

No

350

New England City and Town Area

Yes (within U.S.)

No

500

Congressional Districts - 111th

Yes (within state and U.S.)

No

510

Congressional Districts - 111th - County

Yes (within state)

No

610

State-State Legislative District (Upper Chamber)

Yes (within state)

No

620

State-State Legislative District (Lower Chamber)

Yes (within state)

No

795

Public Use Microdata Areas (PUMAs)

Yes (within state and U.S.)

No

950

Elementary School Districts

Yes (within state)

No

960

Secondary School Districts

Yes (within state)

No

970

Unified School Districts

Yes (within state)

No

NOTES:

1.        The Census Bureau publishes 2005-2009 5-year estimates for many types of geographic areas (aka "geographic summary levels"). Many, but not all of these types of geographic areas are available in DataFerrett. Over time, the remaining types of geographic areas will be added to DataFerrett.

2.        DataFerrett allows the user to create a map showing the distribution of values for any characteristic that can be represented in a column of a DataFerrett table for any type of geographic area which permits mapping (i.e., "Yes" in the column "Thematic Mapping Available?").

3.        Instructions for creating thematic maps in DataFerrett can be found in Chapter 14 of the User Guide, "Making a Map". (url: http://dataferrett.census.gov/support/user/chapter14.html)