Aggregate data Also called summary data tabular data

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: //hsus. cambridge. org/HSUSWeb

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 – NHGIS in the news: http: //chronicle. com/article/Adults-With-College-Degrees-in/125995/

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

Raw Census Microdata from IPUMS

Age Sex Relationship Race Birthplace Mother’s birthplace Occupation IPUMS Data Structure Household record (shaded) followed by a person record for each member of the household For each type of record, specific columns 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