The Integrated Public Use Microdata Series database

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Lab 1 Background on the IPUMS and SPSS
IPUMS www.ipums.org
The Integrated Public Use Microdata Series
database
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Lab 1 Introduction to the datasets

• What is the IPUMS?

? Who uses IPUMS?

• What research is IPUMS best for?

• Other IPUMS-like datasets

• Getting and using the data

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Census Samples Included in the IPUMS
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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.g
ov an occupation table from a published
census volume from the library
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1930 Census Population Schedule, made public
April 2002
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Raw Census Microdata from IPUMS
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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
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The Advantages of Microdata
? Combination of all of a
persons 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
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INTEGRATION
What the IPUMS actually does to the original
census samples
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IPUMS Translation Table for RACE
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IPUMS Translation Table for RELATIONSHIP
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IPUMS Documentation Farm Status Variable
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Additional ways in which IPUMS improves the
original samples
? Additional documentation, including
all enumeration forms and instructions ?
Consistent occupation/industry classifications ?
Consistent metropolitan classifications ?
Constructed family variables ? Locator
variables for spouse and parents
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Lab 1 Introduction to the datasets

• What is the IPUMS?

? Who uses IPUMS?

• What research is IPUMS best for?

• Other IPUMS-like datasets

• Getting and using the data

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Quantity of IPUMS Data Downloaded
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Who uses the data?
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How do people get IPUMS data
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Lab 1 Introduction to the datasets

• What is the IPUMS?

? Who uses IPUMS?

• What research is IPUMS best for?

• Other IPUMS-like datasets

• Getting and using the data

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4 Key Strengths of the Census Microdata Samples
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Limitations of the Census Microdata Samples
1-in-100 samples (1-in-20 for 1970-2000)
Too small to answer some questions
Decennial
Any historical analysis must use 10-year gaps
Cross-sectional data
Not longitudinal
Need knowledge of a statistical package
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What type of question is IPUMS best suited for?

• Studies that do not need to identify geographic
  areas of less than 100,000 after 1940 (e.g.,
  cannot identify Clemson, SC. Can identify a
  group of several counties of which Clemson is a
  part).
• Subjects that are likely to deal with at least
  10,000 people, preferably more. 10,000
  individuals will generate about 100 cases in
  IPUMS. Anything less than this is probably too
  small a sample for useful analysis.
• Any analysis of census-related question that is
  not answered via the published census volumes or
  summary files.

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An example Southern migrants in the
North 1870-1970
Published census volumes can tell you
--How many southern-born persons of each race
lived in each state in 1900, 1920, 1930, and
1960 --occupations of all African-Americans in
the North
But youre also interested in
--The jobs held by actual migrants --How their
jobs compared to those who stayed home --How
their jobs compared to northern-born blacks
--How their settlement changed from 1870 onward
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An example Why this analysis works
The numbers are very large
--over 500,000 southerners are in the North in
every decade from every decade from 1870 on
I dont need to know particular towns
--state of residence is available in every
census --a sub-state designation known as State
Economic Area (SEA) is even available for every
census
Data not available anywhere else
--and so it is worth the trouble
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An example What you cant do with the IPUMS
How did the southerners do in Pittsburgh?
--IPUMS has data on 90 employed southern black
men in Pittsburgh in 1970, fewer in previous
years.
Were the migrants segregated in the north?
--you dont know their street, tract, or
ward --all you know is their city, and only that
if it was a pretty big one (gt100K for 1940-50
and 1980-90 gt250K for 1960-70 gt100K in 2000).
Did migrants jobs improve over time?
--The census samples are cross-sectional
databases, not longitudinal ones
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Lab 1 Introduction to the datasets

• What is the IPUMS?

? Who uses IPUMS?

• What research is IPUMS best for?

• Other IPUMS-like datasets

• Getting and using the data

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Ongoing data projects at the MPC
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Ongoing data projects at the MPC
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Ongoing data projects at the MPC
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Ongoing data projects at the MPC
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Lab 1 Introduction to the datasets

• What is the IPUMS?

? Who uses IPUMS?

• What research is IPUMS best for?

• Other IPUMS-like datasets

• Getting and using the data