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Understanding Census Geography
Lisa Neidert
NPC Workshop: Analyzing Poverty and Socioeconomic Trends Using the American Community Survey
June 22 – June 26, 2009
What’s available in the ACS for single year data: via maps
Maps showing counties and places for each state (or the nation)
http://www.census.gov/acs/www/Products/users_guide/acs_2007_reference_maps.htm
States where all counties are over 20,000
Connecticut Delaware District of Columbia New Hampshire New Jersey Rhode Island
What geographies are available in the 2005-2007 ACS
http://www.census.gov/acs/www/acs-php/2005_2007_beginner_users_guide.php
What’s available in the ACS: via Look-up tables
Geographic entities available for 1-year data (2007)
Geographic entities available for 3-year data (2005-2007)
Not ready for prime-time: census tracts and zip codes
Need 5-year estimates file 2005 – 2009 Available 2010
Annual updates thereafter 2006 – 2010 2007 – 2011, etc.
Test site available – selected counties (34) Selected profiles (demographic, social, economic,
housing) http://www.census.gov/acs/www/AdvMeth/Multi_Year_Estimates/overview.html#noteforusers
Zip codes
Not census geography However, big demand for zip code data
Census Bureau builds ZCTAs via census blocks
ZCTA FAQs http://www.census.gov/geo/ZCTA/
zctafaq.html Fun resource
http://en.wikipedia.org/wiki/Zip_code
What are PUMAs?
Public Use Microdata areas Combination of population geographies
that sum to at least 100,000 population. In rural areas, several counties will form
a PUMA. In an urban area, a county will be subdivided into multiple PUMAs.
PUMAs do not cross state boundaries
PUMAs. . . .
PUMAs do not have good comparability over time (1990, 2000).
PUMA geographies for the ACS are the same as the 2000 boundaries
PUMAs are reasonable substitutes for counties
Smallest geography available in the microdata.
PUMAs
Can be valuable for bypassing geographic restrictions when one wants national information at the county level
Create pseudo counties based on a cross-walk between PUMAs and counties
PUMAs via Maps
Reasonable tool for rural parts of a state Somewhat unwieldy for urban areas Multiple maps per state
http://usa.ipums.org/usa/volii/2000pumas.shtml
PUMAs via text
Describes PUMA composition By:
County County subdivision Place Census tract
http://usa.ipums.org/usa/volii/2000pumas.shtml http://www.psc.isr.umich.edu/dis/data/ref/
PUMA/SUPERPUMA-2000-5pct.html