Aggregate data

• Also called summary data, tabular data• Counts of things for places (e.g. counties) or entities

• Examples: – census volumes– HSUS– ICPSR files– NHGIS

Published Census Volumes

http://www.census.gov/prod/www/abs/decennial/

Historical Statistics of the United States

http://www.cambridge.org/us/americanhistory/hsus/reviews.htm

ICPSR Files 1 and 3

• United States Historical Election Returns, 1824-1968

• Historical, Demographic, Economic, and Social Data: The United States, 1790-1970

– Historical census browser– http://fisher.lib.virginia.edu/collections/stats/histcensus/

NHGIS

– http://www.nhgis.org

– http://www.socialexplorer.com

Uses of aggregate data

• Making pretty maps• Spatial analysis (e.g. residential segregation)• Ecological analysis• Multi-level analysis (or contextual) in combination

with microdata• Aggregate data are often the only alternative

(confidentiality, lost forms)

WHAT ARE MICRODATA?

Individual-level data

• every record represents a separate person • all of their individual characteristics are recorded • users must manipulate the data themselves

Different from aggregate/summary/tabular data

• a disability table from www.factfinder.census.gov • an occupation table from a published census volume

from the library

1930 Census Population Schedule, made public April 2002

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

Raw Census Microdata from IPUMS

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

Relationship

AgeSexRace

BirthplaceMother’s birthplace

Occupation

IPUMS Data Structure

Household record(shaded) followedby a person recordfor each member of the household

For each type of record, specificcolumns correspond to different variables

http://www.rhd.uit.no/nhdc/micro.html

The Advantages of Microdata

Combination of all of a person’s characteristics

Characteristics of everyone with whom a person lived

Freedom to make any table you need

Freedom to make models to look at multivariate relationships