Aggregate data

1. 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

2. Published Census Volumes http://www.census.gov/prod/www/abs/decennial/

3. Historical Statistics of the United States http://www.cambridge.org/us/americanhistory/hsus/reviews.htm

4. 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/

5. NHGIS • http://www.nhgis.org • http://www.socialexplorer.com

6. 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)

7. 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

8. 1930 Census Population Schedule, made public April 2002

9. Raw Census Microdata from IPUMS

10. Age Birthplace Sex Mother’s birthplace Relationship Race 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

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

12. 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