Census 2000: Public Law 94-171 readme file

The following information is the text of the README file which accompanies the Census 2000 Public Law 94-171 dataset.  In addition to the FTP address included in this documentation, you may also download the data from Minnesota Planning's server at:
ftp://www.demography.state.mn.us/mncensus.zip

README File for Census 2000 Redistricting Files Delivered via FTP

Note: Users processing these FTP files in a Windows environment should read carefully the File

Information section of this document.

About the FTP Application

This FTP (File Transfer Protocol) application is intended for experienced users of census data, compressed files, and spreadsheet/database software. It provides quick access to data users, such as State Data Centers and news media, who need to begin their analysis immediately upon data release. Due to the size of the files, the FTP user should have a fast file transfer capability.

Each state directory provides all files available for the identified state. Once uncompressed, the data are in a flat ASCII format. The geographic file is in a fixed-field format; the two data files are in comma delimited format. No software is provided. Users of the FTP application need to unzip the compressed file after downloading, then import it into the spreadsheet/database software of their choice for data analysis and table presentation.

Other Sources of the Data

The Census Bureau releases most Census 2000 data on a state-by-state basis. Tables are available in American FactFinder (factfinder.census.gov) upon release of the designated state file. Within American FactFinder, individual tables can be downloaded in a text delimited or comma delimited format.

For users without immediate need for the data, CD-ROMs containing the data and access software are scheduled for shipping shortly after the state file release. They can be ordered from the Census Bureau's Customer Services Center at 301-457-4100.

FTP Directory

The FTP directory is at http://www2.census.gov/census_2000/datasets/ . When the Census 2000 redistricting data are added to their respective directories, each state directory has three data files, reflecting the three data segments. See below for more information on the data segments.

File Information

Once uncompressed, these files are in flat ASCII format. The geographic header file (see below) contains fixed fields while the data files (File01 and File02, see below), including the geographic link fields, are in comma-delimited format. These files have been constructed in a UNIX environment. They use an ASCII linefeed, chr(10), to indicate a new record.  For successful use with many programs running in a Windows environment, these files need to be modified to use the ASCII carriage return/linefeed sequence, chr(13) + chr(10) as a record terminator. This is an easy step in the Unzip process using any Unzip software which offers the conversion option. We tested PKZIP for Windows, version 4.00 following the steps outlined below. This PKZIP shareware can be downloaded from www.pkware.com. After installing PKZIP, do the following:

--Select the file

--Select the Extract option on the tool bar

--Select the options button at the bottom of the Extract page

--Under the Miscellaneous section, select the "DOS - convert to CR/LF"

The resulting file will meet the ANSI MS-DOS/Windows standard used by Access 97 and other MS Windows-based programs. If the data are being processed in a UNIX environment, they can be unzipped using any standard ZIP/Unzip package.

These FTP data are available as compressed files at the 90% (approximately) file compression ratio. We estimate that an average state FTP download (at 56K bps) of the redistricting data will take approximately 2 hours. Larger states, of course, will take longer. Our estimate for an FTP download for California is approximately 8 hours at the 56K bps speed. If you are using a modem/telephone line link to the Internet, we do not recommend using the FTP option.

Segmented Data

The data in the redistricting files and other Census 2000 summary files are segmented. This is done so that individual files will not have more than 255 fields, facilitating exporting into spreadsheet or database software. In short, to get the complete data set for the redistricting files, users must FTP all three files in the state directory.

These test files contain:

Geographic Header file

File01 (Tables 1 and 2)

File02 (Tables 3 and 4) 

It is easiest to think of the file set as a logical file. However, this logical file consists of three physical files: the geographic header file, file01, and file02. This structure is a change from previous decennial census files. The explanation below for linking the three redistricting test files requires specific location information for the geographic header. These are located in Chapter 7 of the Technical 

Documentation http://www.census.gov/prod/www/abs/pl94-171.pdf . A unique logical record number (LOGRECNO in the geographic header) is assigned to all files for a specific geographic entity; all records for that entity can be linked together across files. Additional identifying fields are also carried over from the geographic header file to the table files. These are file identification (FILEID), state/U.S. abbreviation (STUSAB), characteristic iteration (CHARITER), characteristic iteration file sequence number (CIFSN).

The geographic header record layout is identical across all electronic data products from Census 2000. Since the redistricting data files are quite simple, some of the fields, including some geographic header fields that appear in all three files (geographic header, tables 1/2, and tables 3/4) are not used. For example, the character iteration (CHARITER) field is only used in SF2/SF4. In the redistricting data file, it is always coded as 000.

File Record Layout

For a layout of the individual tables for each file, see http://www.census.gov/prod/www/abs/pl94-

171.pdf . Select Chapter 6, Summary Table Outlines.

Estimated File Sizes

State Geo file File 1 File 2

                      unzip zip      unzip zip        unzip zip

Minnesota   95M 7M       75M 3M        75M 3M