Census Data Resources: Comparing Over Time

Guide to (mostly online) resources for manipulating and extracting Census data.

Comparing Decennial Long Form Data to ACS Data

The American Community Survey: Benefits and Challenges
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Hayslett, M. and Kellam, L. The American Community Survey: Benefits and Challenges. IASSIST Quarterly, vols. 33/4 and 34/1 [double issue], Winter 2009, p. 31-39.

Census 2000 ACS 2005 Comparison Issues
New York State Dept. of Economic Development, State Data Center. "Census 2000 ACS 2005 Comparison Issues," handout. Distributed to the national State Data Center network in September, 2006.

University of Michigan Library Census Guide
This guide links to an Excel spreadsheet listing population and housing items from the Census.
Measuring America: The Decennial Censuses from 1790 to 2000
Subjects included have changed substantially over time. This guide describes all historical Censuses and includes reproductions of enumeration forms.

Some words of caution for making comparisons across censuses:

Boundaries for all Census administrative geographies (tract-level and below) change across censuses.
Some of the questions asked on the census questionnaire have changed over time, as have the ways respondents were instructed to answer.
Time series analysis below the tract level is inadvisable.

Longitudinal Tract Database
Spatial Structures in the Social Sciences at Brown University developed a product for longitudinal analysis. The Longitudinal Tract Database (LTDB) provides estimates using 2010 tract boundaries for a standard set of variables from 1970 through 2000.
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Compiled by GIS Librarians at UNC-Chapel Hill, pre-joined Geodatabase feature classes and tables are available for download, courtesy of Numeric Data Services at NCSU.
NHGIS Time Series Tables
An NHGIS time series table links together comparable statistics from multiple U.S. censuses in one downloadable bundle. A table is comprised of one or more related time series, each of which describes a single summary statistic (e.g., the count of occupied housing units) measured at multiple times (e.g., each census year from 1970 to 2010) at selected geographic levels (e.g., states or counties).

The set of covered statistics, years, and geographic levels varies from table to table according to which categories are available, and at which levels, at different times. Tables may also differ in the method of geographic integration they use to align geographic units across time.