Methodology

Each census year is served through the association of three objects: a SAS system file organizing the data for each census year; a table of variable labels stored using Perl data structures; and a CGI script which parses selected variables and states, writes a SAS control file, and organizes the presentation of the results. Variable labels were taken directly from the machine-readable dictionaries distributed with the data set by ICPSR. Some variables have been created during processing in order to aggregate population or economic characteristics.

Former iterations of this resource used Perl alone to serve the data, but required substantially more manipulation of the data prior to publication on the Web. This lead to errors and proved to be extremely time consuming. The current method not only provides more flexibility for the user, but also requires far less manipulation of the original data files and so, hopefully, produces fewer errors. Data are prepared using a Perl script which reads the dictionary file, writes a database of variable names and labels, and writes a SAS control file to create the system file. No additional manipulation of the data is performed other than standard checks for inconsistencies based upon the column assignments from the data dictionary.

There is, by choice, no Java or JavaScript in any of the following pages. This is in order to try and create a resource compatible with as many browsers as possible. Memory-deprived users and those with slow modems will face challenges when selecting too many variables or trying to view too many states or counties.



The data and terminology presented in the Historical Census Browser are drawn directly from historical volumes of the U.S. Census of Population and Housing.

To Cite This Collection (APA Style)

(2004). Historical Census Browser. Retrieved [Date you accessed source], from the University of Virginia, Geospatial and Statistical Data Center: http://fisher.lib.virginia.edu/collections/
stats/histcensus/index.html.


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