Transcript Understanding Census Geography

Understanding
Census Geography
Lisa Neidert
NPC Workshop: Analyzing Poverty and
Socioeconomic Trends Using the American
Community Survey
June 22 – June 26, 2009
Census Geography
Geographic Areas:
with 1-year and 3-year data
Geographic Areas:
with 1-year and 3-year data
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/Product
s/users_guide/acs_2007_reference_map
s.htm
Counties with single year data:
ACS 2007
Almost all counties:
DE, MA
Few counties, no places:
VT and WY
State with American Indian
Places: AK, AL, LA, NC, OK
Counties with 3-year data:
ACS 2005-2007
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
Geographical Areas (Texas):
Covered in 2005-2007
 ACS 2005-2007 Geographical Areas
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_Estimate
s/overview.html#noteforusers
Example
Census Tracts for community districts
Community District 11:
Manhattan, East Harlem
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.h
tml
 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
Statistics based on 1-year ACS data
Unit is county
Statistics based on 3-year ACS data
Unit is county
Statistics based on 1-year ACS data
Unit is PUMA
Illinois example:
PUMA to county example
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.s
html
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
Metropolitan areas
 Defined by Office Management Budget (OMB)
 http://www.census.gov/population/www/estimat
es/metrodef.html
 Historical Definitions
 http://www.census.gov/population/www/estimat
es/pastmetro.html
 Researcher is free to follow own definitions
 Census Bureau follows OMB definitions