GUIDE TO THE U.S. DECENNIAL CENSUS

History and Background

• Constitutional requirement that every person in nation be counted at least once every 10 years beginning in 1790;
• Primary purpose of the census is to provide population counts for reapportionment in determining number of representatives in the House of Representatives;
• Primary source of data for small geographic areas;
• Many Federal programs distribute funds based upon data from the census, i.e., population, income and employment.

Population Questions

The enumeration of the first census in 1790 was assigned to marshals of the U.S. judicial districts. The enumerators did not have a questionnaire; and in fact, had to supply their own paper. Information was collected for sex, age, and free or slave. From the first census of 1790 through the sixth census of 1840, the household, rather than the individual, was the unit of enumeration for the census. From 1850 forward legislation has continued to make changes in the questionnaires, the procedures and the dissemination of census results.

More detailed information may be obtained from the following sources:

Measuring America: The Decennial Censuses from 1790 to 2000
Includes the questionnaires and instructions to census takers from 1790 to 2000.

Census questionnaires 2000 Includes the short and long form questionnaires; also describes the major differences between the 1990 and 2000 questionnaires.

Factors to Consider when Using the Census

A. Geography

The Census Bureau collects and publishes data for governmental units established by political decision (state, county, city, town, townships) and for statistical units established using criteria developed by the Census Bureau (metropolitan statistical areas, census tracts, and census blocks).

Governmental Units
During the 19th century the boundaries of states, territories, counties, towns, and townships may have changed from one census to the next. Familiarize yourself with the history of the region for which you are gathering data. Changes in county and city boundaries in some states have continued into the 20th century.
The Map Guide to the U.S. Federal Censuses, 1790-1920, by William Thorndale and William Dollarhide, Baltimore, MD: Genealogical Publishing Co., Inc. shows state and county boundary changes from 1790 to 1920.

Census designated place was a new term in 1980, replacing unincorporated places, used for 1970 and earlier censuses. Census designated places are residential concentrations whose population considers itself belonging to a geographically defined place although the place may not be incorporated.

Census tract is the unit for which the Census Bureau attempts to maintain comparability from census to census. The census tract is a statistical subdivision whose average population is 4,000. Prior to 1980 only metropolitan areas were tracted; however, in 1980 five states were entirely tracted and in 1990 tracts were defined for the entire country.

The first census which defined census tracts was the 1910 census; eight cities were tracted. The same eight cities were tracted in 1920; 18 in 1930; and 60 cities in 1940. Prior to 1940 the cities paid for the tabulations.

Census block is the smallest unit for which data is collected. Only the 100 percent data (see below for explanation) is available for this level of census geography.

For more information, consult:

Geographic Concepts

B. Definitions

Changes have occurred in the racial definitions used by the Census Bureau during the last two hundred years. Early censuses collected some data items only for white persons with all other races aggregated. The 1850 census was the first separate enumeration of data for African-Americans; the 1860 census first included American Indians and Chinese; the 1870 census included Japanese; and 1970 was the first enumeration for Spanish/Hispanic Origin. In the 2000 census individuals were allowed to indicate more than one racial category so the number of race and ethnicity tables were greatly increased.

There also have been changes in the definition of family/household and head of household/householder. In 1950 a family was distinguished from a household in that the family represented a group of two or more persons related by blood, marriage or adoption. Prior to 1980 the questionnaire referred to the head of the household and the head of the household was assumed to be male. The 1980 census introduced the term householder and was assumed to be the person completing the form.

The Census Bureau first established metropolitan areas and urbanized areas in 1950. The current definition of a metropolitan area is a large population nucleus, together with adjacent communities that have a high degree of economic and social integration with the core area; it must include an incorporated place, census designated place or minor civil division with a population of at least 50,000. An urbanized area consists of one or more central places and the adjacent densely populated territory that total at least 50,000.

The Census Bureau categorizes all territory, population, and housing as either urban or rural. Urban comprises all territory, population and housing in urbanized areas or in places with population greater than 2,500 outside an urbanized area. All other territory, population, and housing are categorized as rural. From 1920 through 1960 rural was further categorized as rural farm, those living on farms; and rural non-farm, those living in incorporated places of 2,500 or less.

A current list of Metropolitan and micropolitan areas is available.

C. 100% (Short Form) and Sample (Long Form) Questions

The 1940 census provided the prototype for the census today. It was the first census to develop and apply sampling techniques, thus creating the short form or 100% questionnaire and the long form, or the sample. Over the last 50 years the Census Bureau has continued to refine its sampling techniques but the terms 100% or sample are still the same.

In 1990, the 100% population questions related to household relationship, sex, race, age, marital status and Hispanic origin; and the 100% housing questions included number of units in structure, number of rooms in unit, tenure (owned or rented), value of home or monthly rent paid, congregate housing (meals included in rent), and vacancy characteristics.

The sample population component included social characteristics, such as place of birth, education, ancestry, migration, language, veteran status, disability and fertility; and economic characteristics, such as labor force, place of work and journey to work, year last worked, occupation, industry and class of worker, work experience and income. The sample housing components included year moved into residence, number of bedrooms, plumbing and kitchen facilities, telephone in unit, vehicles available, heating fuel, source of water, year structure built, condominium status, farm residence, and shelter costs, including utilities.

The questions asked on both forms have changed over time; they reflect the changes in our society and the need for statistical data mandated by Federal legislative programs. See the Major Differences in Subject-Matter Content between 1990 and 2000 Census Questionnaires.

Census 2000 Questionnaires

D. Historical Comparability

When conducting research using the decennial population and housing censuses, historical comparability must always be considered. Changes may have occurred in the political boundaries, the statistical geographic area definitions, the racial and household definitions, and the content of questions asked. For an overview of these changes, consult the following:

Measuring America: the Decennial Censuses from 1790 to 2000.

Encyclopedia of the U.S. Census, edited by Margo J. Anderson, and published Washington, DC: Congressional Quarterly, 2000, is a good resource. [GDIC Ref. HA37 U55 C66 2000 (LC)]

Introduction: Federal Censuses, in Map Guide to the U.S. Federal Censuses, 1790- 1920, edited by William Thorndale and William Dollarhide. Baltimore, MD: Genealogical Publishing Co., Inc., 1987. [GDC,REF G1201 F7 +T5 1987 (LC)]

Census 2000 Glossary

Census Products Prior to 1990

Prior to 1990 the results of the decennial population and housing censuses were available in print and/or microform. The Summary Tape Files were only available on computer tape. From 1950 forward the population census generally consisted of four reports for each state:

• number of inhabitants
• general population characteristics
• social and economic characteristics
• detailed population characteristics

The housing census was published for each state in the following reports:

• general housing characteristics
• metropolitan housing characteristics

In addition there were census tract (sample) reports and census block (100%) reports.

All of the census publications are available in hard copy with the exception of the following, which at Yale must be used in microform:

1980: Census Blocks on microfiche

The major census volumes for the 1790-2000 censuses are shelved in the Reading Room of the Government Documents and Information Center. The classification numbers for the censuses from 1790 forward are as follows:

1790: I 2.

1800: I 3.

1810: I 4.

1820: I 5.

1830: I 6.

1840: I 7.

1850: I 8.

1860: I 9.

1870: I 10.

1880: I 11.

1890: I 12.

1900: I 13.

1920: C 3.28:

1930: C 3.37/5:

1940: C 3.940-2:P81/

1950: C 3.950-7/2:

1960 & later: C 3.223:

For a more detailed description of the contents of each volume of the 19th and 20th century decennial censuses, consult the following guides:

• Population Information in Nineteenth Century Census Volumes, by Suzanne Schulze. Phoenix, AZ: Oryx Press, 1983. [GDC,REF Z7164 D3 +S441983 (LC)]
• Population Information in Twentieth Century Census Volumes: 1900-1940, Suzanne Schulze. Phoenix, AZ: Oryx Press, 1985. [GDC,REF Z7164D3 +S45 1985 (LC)]
• Population Information in Twentieth Century Census Volumes: 1950-1980, Suzanne Schulze. Phoenix, AZ: Oryx Press, 1988. [GDC,REF Z7164D3 +S45 1988 (LC)]

Internet Resources

Historical Decennial Censuses, Census of Population and Housing
For now the decennial censuses from 1790 through 1860n are available. Additional files will be available as they are digitized.

Selected Historical Decennial Census Population and Housing Unit Counts

Historical, social, economic and demographic data from the U.S. Decennial Censuses, 1790 through 1860 has been made available through the Inter-University Consortium for Political and Social Research (ICPSR) tapes. Data is available for the state and for the counties in most states.

1990 Census

The 1990 Census of Population and Housing was disseminated in printed products and compact discs. For the first time the Summary Tape Files were made available to depository libraries; the format for these was compact disc. The Summary Tape Files provide the level of detail which formerly was only available through the use of the computer tapes. Data may be easily obtained using a menu-driven software program or extracted for use with other statistical software packages.

Printed Products (1990)

• Population: Number of Inhabitants; General Population Characteristics; Social and Economic Characteristics, Census Tract Reports.
• Housing: General Housing Characteristics, Detailed Housing Characteristics, Population and Housing Characteristics for Congressional Districts

Compact Disc Products

• Summary Tape File 1A: 100 percent population and housing counts and characteristics;
• Summary Tape File 1B: 100 percent population and housing data at the block level; (Machine 4)
• Summary Tape File 3A: Sample population and housing characteristics or states and their sub areas including census tracts; (Machine 4)
• Summary Tape File 3B: Sample data weighted to represent the entire population---Zip Code Area data; (Machine 4)
• Summary Tape File 3C: Sample data weighted to represent the entire population---United States, States and Metropolitan Areas; (Machine 4)
• Summary Tape File 3D: Sample data weighted to represent the entire population---Congressional District data.

CensusCD + Maps (GeoLytics) provides every data item from the Summary Tape Files 3A, 3B, 3C, and 3D for the entire nation, down to the block group level on a single disc. The disc also includes geocode indexes from the Tiger/Line files thus allowing you to search on street names. There is also a feature that allows you to create maps of your data. Compact discs are now available at the Government Documents and Information Center for the 1970, 1980, 1990 and 2000 censuses.

For more information regarding the 1990 publication program, consult the following: 1990 Census of Population and Housing Tabulation and Publication Program. Washington, DC: U.S. Bureau of the Census, 1989. [GDC,REFC 3.2:T11/2]

Most of the 2000 census data was only released electronically. For information on the 2000 publication program, consult Census 2000 Products at a Glance or connect to Your Gateway to Census 2000.

Internet Resources

Information about and from the 1990 Census of Population and Housing is available from several internet sites. The Bureau of the Census provides the American Fact Finder. Information for both 1990 and 2000 census; State & Country QuickFacts--provides profiles of states and counties; or generate maps using the TigerFiles. The URL for the main Census home page is: http://www.census.gov

Census data from the 1990 Census of Population and Housing for New Haven, Connecticut, is available at the following site: New Haven Demographics

Users who need to work with a number of geographic areas and multiple variables may find it easier to work with the 2000 census data from ICPSR. Earlier census data is also available from ICPSR (Inter-University Consortium for Political and Social Research).

The Government Documents and Information Center's home page provides links to these and other locations for statistical data.