Tracking the Decennial Census

What's the Purpose of the Census?

Established by the Constitution in 1787 in order to provide for the regular reapportionment of congressional districts and direct taxes, the decennial census has reflected the growth and development of the United States. Census-takers no longer go door to door regularly to interview people and record their responses; the census forms are now largely mailed out, filled in, and processed by computer, and the data originally published in paper volumes has now been distributed on DVD-ROM and made available online from the Census Bureau. Questions are no longer limited to the number of persons in a household but now include specific breakdowns of population by age, race, and sex as well as more detailed information such as educational attainment, occupation, and income.

There are two forms of the census questionnaires: a short form containing basic population and housing questions, and a long form containing the same basic questions along with additional, more detailed questions on housing, social, and economic subjects. Those questions asked on the short forms and thus answered (theoretically) by all citizens are referred to as "100%" questions, while those asked only on the longer form (sent to roughly 1/6 of the population) are referred to as "sample" questions. For information on how the questions have changed from 1790 to the present, see Measuring America: The Decennial Censuses from 1790 to 2000.

The Organization of Our Collection

The College of Wooster's decennial census collection can be found in a separate collection called Document Ref. Census, located at the south end of the Document Reference collection on Andrews 1. Because the classification of these volumes changed multiple times over the years, we have established an in-house classification system that we hope will make it easier to find census volumes.

Decennial census volumes are arranged first by date of census so that all the materials are in chronological order. From 1790 to 1920, there is very little complexity in arranging the statistics, so after an abstract or compendium volume, the volumes of statistics are shelved in volume number order. From 1930 onward, volumes within a census are arranged alphabetically by section of the census (agriculture, housing, population, etc.) and by series (census tracts, characteristics, etc.). For example:

1940 / A / Irrigation
1940 / A / v.2 / pt.1
   (A stands for Census of Agriculture)

1970 / PH / Census Tracts / v.1
   (PH stands for Population & Housing)

Please note that the decennial census data for 1990 and 2000 that are available on CD-ROM and DVD-ROM have not been reclassed and are still located in the Document Ref. Electronic collection under their original Census Bureau call numbers.

Census Geography

Census geographical terms define various areas from as large as the national level down to the block level for collecting statistics. A simplified summary of the hierarchy of census geography, from largest area to smallest, would look like this:

Nation
State
County
Census Tract or Block Numbering Area
Block Group
Block

Many other geographical terms used by the Census Bureau can overlap these basic areas, including metropolitan areas, places, and congressional districts. Although these terms tend to remain stable over decennial censuses, their boundaries may change and other terms may be used, so it is always a good idea to familiarize yourself with the geography appendix (Appendix A for 1970-1990, separate volume for 2000) for a particular decennial census before attempting to use the statistics.

Definitions of some basic geographic terms include:

• Block: The lowest level of census geography used in data tabulation.
• Block Group: A cluster of blocks, consisting of an average of 400 housing units.
• Block Numbering Area: A small county subdivision consisting of a large number of blocks; equivalent to census tracts in nonmetropolitan areas.
• Census Tract: A small, locally delineated area within metropolitan and other densely populated areas; designed to be homogeneous in terms of demographic characteristics, tracts usually have between 2500 and 8000 persons living within their boundaries.
• County: The primary political division of most states; equivalents include parish (in Louisiana), independent city (in Maryland, Missouri, Nevada, Virginia), municipio (Puerto Rico).
• Metropolitan Area: A county or group of counties containing a large population nucleus of at least 50,000 inhabitants (or at least 100,000 inhabitants if more than one population nuclei); contiguous counties are included if they have close social and economic links with the population center. Variant terms include consolidated metropolitan statistical area (CMSA) for two or more large cities combined and primary metropolitan statistical area (PMSA) for the population center.
• Place: A concentrated population area (city or town) with legally designated boundaries; unincorporated areas may be defined as the rough equivalent census designated place (CDP) but may be more subject to change.
• State: The primary governmental division of the United States; areas such as the District of Columbia and outlying areas like Puerto Rico or Guam are considered as state equivalents.

Where to Find Your Data

We hope that our classification system will make it easier for you to find your data in the later, more extensive decennial census series.

• For basic figures for population or housing from the 100% forms
  Characteristics or General Characteristics volume for your year and section (population or housing); for 2000, check the PH / Sum. Pop. Housing volumes



• For sample data for the larger geographic areas (nation, state, county, place)
  Characteristics or Detailed Characteristics volume for your year and section; for 2000, check the PH / Sum. Social volumes



• For statistics specific to smaller geographic areas (1960-1990)

  Block statistics:	(year) / H / Block Stats / vol.
  Census tract statistics:	(year) / PH / Census Tracts / vol.
  Metropolitan area statistics:	(year) / H / Metropolitan / vol.

Data for the 2000 census is also available online through American FactFinder and copies of earlier decennial census reports (PDF files) can be found at http://www.census.gov/prod/www/abs/decennial/index.htm.

Other Resources for Using the Census

For more detailed information on using the decennial censuses, or for additional statistics, please use the following recommended links:

• American FactFinder and Census 2000 (University of Michigan)
• Census Index (Ohio State University)
• Census Information (St. Mary's University, Texas)
• Census 2000 at ICPSR
• Census 2000 Tutorial (by Daniel Cornwall, Alaska Library Association)
• Historical Census Browser
• Office of Strategic Research (Ohio data)
• State & County Quick Facts