Transcript Data from the Census Bureau: Censuses, Surveys & Tools

Census 2010: Census
Geographies from Large to Small
Tuesday, July 26, 2011
10-11:30am
Placeholder
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Summarize key points from last week related
to geography
Quick Review: Week 1 topics
Census Data includes both numeric data – (e.g. aggregate data
and microdata) -- as well as also geographic boundaries
Aggregate data released in a variety of products, differing in
content, geographic specificity and temporal coverage
Microdata has flexibility of individual level information, but
balances this by only gross geographic detail
Resources exist to aid researchers in associating numeric data
with geographic boundaries, harmonizing data over time, and
harmonizing geographies over time.
Topics for Today
What are “census geographies?
How are they defined?
What are their characteristics?
How do they relate to one another?
What data is available for Census geographies?
For what periods is data available?
What kinds of data are available?
How have census geographies changed and why do those
geographies change?
What resources exist for tracking down geographies, relationships
and data?
Basic Census Geography
Legal/Administrative
Entities
Statistical
Entities
Nested Geographies: Regions
Groupings of states and the District of Columbia that
subdivide the United States.
There are four census regions—Northeast, Midwest,
South, and West.
Before 1984, the Midwest region was named the North
Central region. From 1910 (when census
regions were established) through the 1940s, there
were three census regions—North, South, and
West.
Data for Regions available for Decennial Census,
Economic Census, Agriculture Census, ACS 1/3/5 year
Nested Geographies: Divisions
Each of the four census regions is divided into two or
more census divisions. There are nine census divisions,
which the U.S. Census Bureau established
in 1910.
Data for Divisions available for Decennial Census,
Economic Census, Agriculture Census, ACS 1/3/5 year
Nested Geographies: States
States are the primary governmental divisions of the
United States. The District of Columbia is
treated as a statistical equivalent of a state for data
presentation purposes. (As were American Samoa, the
Commonwealth of the Northern Mariana
Islands, Guam, Puerto Rico, and the Virgin Islands of
the United States – in the 2000 tabulations.)
Data for States available for Decennial Census,
Economic Census, Agriculture Census, ACS 1/3/5 year.
Census Regions and Divisions of the United States
Nested Geographies: Counties
The primary legal divisions of most states are termed
‘‘counties.’’
Counties in 48 States
Independent Cities in 4 States
Parishes in Louisiana
Cities and Boroughs in Alaska
Smallest consistently defined legal/administrative
geography with national coverage.
Data for counties available for Decennial Census,
Economic Census, Agriculture Census, City/County
Databooks, County Business Patterns, Census of
Governments, Human Area Resource Files, Criminal
Justice data, Federal Outlays, ACS 1 year (25%), 3 year
(60%).
Nested Geographies: Counties
Nested Geographies: Census Tracts
Census tracts are small, relatively permanent statistical
subdivisions of a county or statistically
equivalent entity.
The primary purpose of census tracts is to provide a stable
set of geographic units for the presentation of decennial
census data. They are typically delineated by a committee
of local data users. Generally, census tracts have between
2,500 and 8,000 residents and boundaries that follow
visible features.
When first established, census tracts are to be as
homogeneous as possible with respect to population
characteristics, economic status, and living conditions.
The 2000 census was the first census for which the entire
county was tracted. In earlier years, Block Numbering
Areas (BNAs) provided sub-county geography for untracted
areas.
Data for Tracts available for Decennial Census, ACS 5
year.
Historical Census Geography
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Census Tracts
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First created in 1910
8 cities tracted and 1910 and 1920
By 1940, 60 cities tracted
Substantial increase in tracting with advent of
Metropolitan Areas in 1950
Entire nation tracted/BNA’d by 1990
Tracts can split/merge
Nested Geographies: Block Groups
A census block group (BG) is a cluster of census
blocks having the same first digit of their four-digit
identifying numbers within a census tract. BGs
generally contain between 600 and 3,000 people, with
an optimum size of 1,500 people.
Data for BGs available for Decennial Census, ACS 5
year (selected tables).
Nested Geographies: Blocks
A block is the smallest geographic unit for
which the Census Bureau tabulates data. Many blocks
correspond to individual city blocks bounded by
streets, but blocks – especially in rural areas – may
include many square miles and may have some
boundaries that are not streets.
A census block is an area normally bounded
by visible features, such as streets, streams, and
railroads, and by nonvisible features, such as the
boundary of an incorporated place, county (borough or
census area), or other Census 2000 tabulation entity.
Census blocks typically contain around 100 persons.
Tabulation blocks do not cross the boundaries
of any entity for which the U.S. Census Bureau
tabulated data.
Basic Census Geography
Non-Nested Geographies - Place
Places, for the reporting of decennial census data, include census
designated places (CDPs), and incorporated places. Places nest
within states, but their boundaries can cross other sub-state
geographies, including census tracts and BGs.
Incorporated places recognized in decennial census data products
are those reported to the U.S. Census Bureau as legally in
existence on January 1, 2000, under the laws of their respective
states, as cities, boroughs, city and boroughs, municipalities,
towns, and villages. (See the GARM for a summary of state
requirements for incorporated places as of 1990). No minimum or
maximum size except by statute. The size of places (both in
population and land area) varies dramatically: the smallest place in
1990 had population less than 10, while the largest had population
greater than 7 million.
Boundary changes identified from the BAS (Boundary and
annexation Survey), conducted annually since 1972.
Boundary & Annexation Survey
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The U.S. Census Bureau conducts an annual survey called the Boundary and
Annexation Survey (BAS) to collect information about selected legally defined
geographic areas, such as counties (and equivalent areas), incorporated
places, minor civil divisions (MCDs), as well as federally recognized American
Indian reservations (including off-reservation trust lands and tribal
subdivisions).
The place BAS rotates the incorporated places surveyed each year:
In years ending in 1,3,4,5,and 6, the BAS includes only incorporated places
with a populations of 5,000 or greater.
In years ending in 2 and 7 the population threshold is lowered to 2,500.
In the three years before the decennial census, all incorporated places are
included in the BAS regardless of size.
In any BAS year, the Census Bureau will include some special areas, such as
any newly incorporated places, places which have had an unusual change, or
places needed for a special Census Bureau operation scheduled for that year.
Non-Nested Geographies - CDPs
Census designated places (CDPs) are delineated for each
decennial census as the statistical counterparts of incorporated
places. CDPs are delineated to provide census data for
concentrations of population, housing, and commercial structures
that are identifiable by name but are not within an incorporated
place. CDPs exist in all states.
Census designated places (CDPs) are closely settled, named,
unincorporated communities that generally contain a mixture of
residential, commercial, and retail areas similar to those found in
incorporated places of similar sizes. These communities do not
have legally defined municipal boundaries or corporate powers.
The Census Bureau works with local participants to delineate
boundaries for CDPs.
CDPs can’t be contained, in whole or part, within an incorporated
place (or another CDP). Prior to 2000, CDPs had a minimum
population threshold of 1000; no current minimum.
Historical Census Geography
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Places
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State-specific requirements for incorporation
In 1950, CDPs introduced by Census (called
unincorporated places).
Increase in size due to annexations
Increase in numbers due to incorporation
Merging of places possible
Between 1980 and 1990, 40% of places
experienced some change in boundary
Basic Census Geography
Non-Nested Geographies – County Subdivisions
These are the primary geographic units recognized by the Census
Bureau which are just below the county level. The primary
distinction drawn between these subdivisions is between Minor
Civil Divisions (MCDs) and Census County Divisions (CCDs).
Most states have Minor Civil Divisions (MCD's) which are legally
recognized governmental or administrative units. MCD's are
defined in 28 states and in D.C. The specific types of MCD's vary
by state. The most common type of MCD is the township, but also
include towns or incorporated places, assessment districts,
election districts, plantations, magisterial districts, etc.
Boundary changes identified from the BAS (Boundary and
annexation Survey), conducted annually since 1972.
In the remaining states the Census Bureau has defined Census
County Divisions (CCD's). (The types of county subdivisions by
state are identified in the GARM, Table 8-2.)
Non-Nested Geographies – County Subdivisions
The primary goal of delineating CCDs is to establish and
maintain a set of subcounty units that have stable boundaries
and recognizable names. A CCD usually represents one or more
communities, trading centers or, in some instances, major land
uses. It usually consists of a single geographic piece that is
relatively compact in shape. The geographic "building blocks" of
CCDs are census tracts, and many CCDs are groupings of
several contiguous census tracts. (Although in some rural
counties, two or more CCDs may next within a tract).
New CCDs should have a minimum population of 1,500 persons.
Some existing CCDs may have smaller populations. There is no
maximum population size limit for a CCD.
Each state has either all MCD's or all CCD's - there is never a
split. In the geographic hierarchy these divisions provide
a complete coverage of all counties in the county. There were
more than 36,000 such geographic areas in the U.S. at the time of
the 2000 census.
Basic Census Geography
Non-Nested Geographies – CBSA’s
Core Based Statistical Areas (CBSAs) consist of the county or
counties or equivalent entities associated with:
•
at least one core (urbanized area or urban cluster) of at
least 10,000 population,
• plus adjacent counties having a high degree of social and
economic integration with the core as measured through
commuting ties with the counties associated with the core.
The term "core based statistical area" became effective in 2003 and
refers collectively to metropolitan statistical areas and micropolitan
statistical areas.
Non-Nested Geographies – CBSA’s
Basic subclassification of a CBSA is into a Metropolitan Statistical
Area (MSA) or a Micropolitan Statistical Area (μSA). Statistical
Areas (SAs) may be part of a higher order Combined Statistical
Area (CSA) or standalone. Collectively, the CSAs and standalone
MSAs and μSAs are known as Primary Census Statistical Areas
(PCSAs)….
(and just to make this a bit more complicated…)
MSA’s may be subdivided under some circumstances in
Metropolitan Divisions (MDs).
Also, in general the SA’s are aggregates of counties, but for New
England, they can be combinations of cities, towns and counties.
Versions of SA’s for New England based on (the more historically
consistent) non-county boundaries are called New England city
and town areas (NECTAs).
…..which are the flip side the older New England countybased areas called New England County Metropolitan Areas
(NECMAs).
Non-Nested Geographies – CBSA’s
MSAs (366)
μSAs
(576)
CSAs (125)
Standalone MSAs (186)
Standalone μSAs (407)
PCSAs (718)
Non-Nested Geographies – Metropolitan Areas
Metro Areas: Now subsumed under CBSA – Core-based Statistical Area
Metropolitan Areas are intended to be composed of a “core area
containing a large population nucleus, together with adjacent
communities that have a high degree of economic and social
integration with that core”.
Metropolitan areas (as their first incarnations as SMAs) were first
defined for the 1950 census, but were preceded by metropolitan
districts in 1910 through 1940. These predecessors to
metropolitan areas were principally defined on the the basis of
population density, and were composed of aggregates of subcounty geographic units.
The MAs defined in 1950 were (except in New England) composed
of whole counties, and a corresponding unit – the urbanized area –
was defined on the basis of population density to provide a greater
distinction based on densely built up areas around the core cities.
The proportion of the population living in MA’s has grown substantially since
they were first reported in 1950. This growth has more to do with the creation
of new MA’s than with movement into existing MA’s.
Percent of US Population Living in:
1960
1970
1980
1990
1998
MAs as defined in 1950
59.3
60.1
56.9
56.2
54.9
MAs as defined in 1960
63.0
64.4
62.1
62.4
61.6
MAs as defined in 1970
66.7
68.6
66.9
67.5
67.1
MAs as defined in 1980
73.2
75.6
74.8
75.9
76.0
MAs as defined in 1990
74.3
76.8
76.2
77.5
77.7
MAs as defined in 1998
80.1
Non-Nested Geographies – Metropolitan Areas
If an area that qualifies as a metropolitan area (MA) has 1 million
people or more, two or more primary metropolitan statistical
areas (PMSAs) may be defined within it. Each PMSA consists of a
large urbanized county or cluster of counties (cities and towns in
New England) that demonstrate very strong internal economic
and social links, in addition to close ties to other portions of the
larger area. When PMSAs are established, the larger MA of which
they are component parts is designated a consolidated
Metropolitan statistical area (CMSA). CMSAs and PMSAs are
established only where local governments favor such
designations for a large MA.
An accompanying statistical area -the micropolitan area – was
implemented in 2003. A micro area contains an urban core of at
least 10,000 (but less than 50,000) population. Each micro area
consists of one or more counties and includes the counties
containing the core urban area, as well as any adjacent counties
that have a high degree of social and economic integration (as
measured by commuting to work) with the urban core. The
bureau has identified 578 such areas in the nation.
Basic Census Geography
Non-Nested Geographies – Urban Areas
Urban and Rural:
Urban places are defined starting with a block
group (tract in 2010) that has a population density
of 1,000 persons per square mile and adding on
block groups and blocks that have a density of 500
persons per square mile (within a particular “jump”
distance).
If the territory so defined has 2,500 or more people,
it is then called an "Urban Area."
Urban Areas are called Urbanized Areas if they have
50,000 or more people and Urban Clusters if they
have between 2,500 and 49,999 people.
All other areas are rural.
Basic Census Geography
Non-Nested Geographies – ZCTAs
A ZIP Code tabulation area (ZCTA) is a
statistical geographic entity that
approximates the delivery area for a U.S.
Postal Service five-digit or three-digit ZIP
Code. ZCTAs are aggregations of census
blocks that have the same predominant
ZIP Code associated with the residential
mailing addresses in the U.S. Census
Bureau’s Master Address File. Three-digit
ZCTA codes are applied to large
contiguous areas for which the U.S.
Census Bureau does not have five-digit
ZIP Code information in its Master
Address File. ZCTAs do not precisely
depict ZIP Code delivery areas, and do
not include all ZIP Codes used for mail
delivery.
Non-Nested Geographies – ZCTAs
Average ZCTA size is about 9000 in the 2000 census
Data for ZIP code include Decennial Census,
Economic Census, ZIP Business Patterns
(http://www.census.gov/epcd/www/zipstats.html)
Census Geographies and the ACS
Census Geographies and the ACS
Geographic grain and Margin of Error
Margin of Error: Example, Selected California Geographies/Periods
Percent in Poverty
Margin of Error: Example, Selected California Geographies/Periods
Percent in Poverty
Significance testing
1. Get the Margin of Error (MOE) from ACS
2. Calculate the Standard Error (SE)
[SE = MOE / 1.645]
3. Solve for Z where A and B are the two
estimates
AB
Z
(SE(A))2  (SE(B)) 2
4. If Z < -1.645 or Z > 1.645
Difference is Significant at 90% confidence
Micro-data Geographies
Non-Nested Geographies – PUMAs
A public use microdata area (PUMA) is a decennial census area for
which the U.S. Census Bureau provides specially selected extracts of
raw data from a small sample of long-form census records that are
screened to protect confidentiality. These extracts are referred to as
‘‘public use microdata sample (PUMS)’’ files. For Census 2000, two two
types of PUMAs were delineated within states.
PUMAs of one type comprise areas that contain at least 100,000 people.
The PUMS files for these PUMAs contain a 5-percent sample of the
long-form records. The other type of PUMAs, super-PUMAs, comprise
areas of at least 400,000 people. The sample size is 1 percent for the
PUMS files for super-PUMAs.
PUMAs cannot be in more than one state or statistically quivalent entity.
The larger 1-percent PUMAs are aggregations of the smaller 5-percent
PUMAs. PUMAs of both types, wherever the population size criteria
permit, comprise areas that are entirely within or outside metropolitan
areas or the central cities of metropolitan areas.
Non-Nested Geographies – PUMAs
The geographies associated with Public Use Microdata Samples
(PUMS) differ from census to census and, within census, by the type of
sample.
Examples: 1970: 6 samples, State, Metro (250K), Neighborhood
1980: State, Metro (100K) samples
1990: State, Metro (100K) samples
Some Key Points to Remember
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Census Geographies include nested and nonnested geographies
Some geographies defined politically, others for
statistical and reporting purposes
Geographies range in size from a block to the
nation as a whole, but different sorts of data
available depending on type of geography
Boundary Files
http://www.census.gov/geo/www/reference.html
Questions/Comments
email me at: [email protected]
http://ucdata.berkeley.edu