Integrating ACS with the World’s Census Data:
ACS Microdata and the IPUMS
Presented at the Pre-ALAP ACS/IPUMS Workshop
November 16, 2010
Trent Alexander
American Community Survey Office
U.S. Census Bureau
Outline
American Community Survey (ACS)
• Overview and ACS PUMS
Integrated Public Use Microdata Series (IPUMS)
• How the ACS PUMS fits in
ACS and the world’s population data heritage
• Does the ACS model work?
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Microdata versus Summary Data
Microdata
Summary Data
• “Raw” data containing
each person’s responses
• Premade or published
tables
• Enables custom tables and
analyses
• Enables examination of
small geographic areas
• Limitations:
geographic identifiers,
fewer cases, less reliability
• Limitations:
limited content
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Summary Data
Source: 2009 ACS 1-year Estimates. Table B15003. EDUCATIONAL
ATTAINMENT FOR THE POPULATION 25 YEARS AND OVER 4
Universe: POPULATION 25 YEARS AND OVER.
Microdata
Source: 2000 Census PUMS.
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Microdata
Source: 2000 Census PUMS.
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Overview of the ACS
• An on-going nation-wide survey providing
reliable annual data
• Conducted in every town and county
• Includes housing units and group quarters
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Basic ACS statistics
• Samples approximately 2.9 million addresses
per year
• 21 questions about housing unit
48 questions about each person
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ACS Data Products
• Similar to decennial “long form” data
• About 1,000 tables for each geographic area
– for 370,000 areas in newest data
• Annual PUMS samples for ~1% of population
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Person records Person records
in ACS PUMS in ACS complete
(millions)
data (millions)
2001
2002
2003
2004
2005
2006
2007
2008
2009
1.2
1.2
1.2
1.2
3.0
3.0
3.0
3.0
3.0
1.3
1.3
1.3
1.3
4.5
4.5
4.5
4.5
4.5
Population
(millions)
285
287
290
293
296
298
301
304
307
Source: B00001. UNWEIGHTED SAMPLE COUNT OF THE POPULATION Universe: TOTAL POPULATION. B01001. SEX BY AGE - Universe: TOTAL
POPULATION
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How does this compare to a
decennial census PUMS?
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Census 2000
PUMS
Geographic Detail
ACS
PUMS
Areas of 100,000+
% Sample per decade
6%
10%
Data collection period
~4 months
1+ years
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Less obvious benefits of ACS
• Permanent staff
– high-quality data collection
– consistent standards for processing, editing, etc.
• Changes are infrequent and well-documented
• Ongoing support for products
• Ability to fix errors and make improvements
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What do PUMS users think?
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IPUMS – Public Data Samples
Integrated - consistent codes, labels, and documentation
Public Use - anonymized, downloadable
Microdata - individual-level
Series - pooled data over time and place
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http://www.ipums.org/
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IPUMS-USA
• Samples from United States and Puerto Rico
• U.S. decennial census and ACS data,1850-2009
• Various specialty samples (longitudinal, oversamples)
• ACS PUMS availability
• All ACS samples from 2000-2009
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ACS in IPUMS-USA:
Extremely popular
• Most requested IPUMS-USA sample this year:
2008 ACS PUMS
• About half of all extracts include ACS data
• 2nd most common search term leading to website:
“ipums acs” (most common is “ipums”)
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IPUMS-International
• World’s largest collection of public census data
• Has 159 census samples from 55 countries
• Incorporating latest censuses and new countries
• ACS PUMS availability
• 2005 ACS PUMS only
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ACS in IPUMS-International:
Not as popular
• 2005 ACS not among the most requested samples
• U.S. Census 2000 requested much more often than ACS
• Will this change when 2010 round of censuses is posted?
• Should IPUMS-Intl include 2010 ACS 1-year data
or 2006-2010 pooled 5-year data?
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Contact Information
Trent Alexander
j.trent.alexander@census.gov
ACS User Support
acso.users.support@census.gov
IPUMS User Support
ipums@pop.umn.edu
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