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Census 2010: Census Geographies from Large to Small
Tuesday, July 26, 2011 10-11:30am
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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 Census Data includes both numeric data – (e.g. aggregate data and microdata) -- as well as also geographic boundariesand microdata) -- as well as also geographic boundaries
Aggregate data released in a variety of products, differing in Aggregate data released in a variety of products, differing in content, geographic specificity and temporal coveragecontent, geographic specificity and temporal coverage
Microdata has flexibility of individual level information, but Microdata has flexibility of individual level information, but balances this by only gross geographic detailbalances this by only gross geographic detail
Resources exist to aid researchers in associating numeric data Resources exist to aid researchers in associating numeric data with geographic boundaries, harmonizing data over time, and with geographic boundaries, harmonizing data over time, and harmonizing geographies over time.harmonizing geographies over time.
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?
Topics for Today
Basic Census Geography
Legal/Administrative Entities
Statistical Entities
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 censusregions were established) through the 1940s, there were three census regions—North, South, andWest.
Data for Regions available for Decennial Census,Economic Census, Agriculture Census, ACS 1/3/5 year
Nested Geographies: Regions
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 establishedin 1910.
Data for Divisions available for Decennial Census,Economic Census, Agriculture Census, ACS 1/3/5 year
Nested Geographies: Divisions
States are the primary governmental divisions of the United States. The District of Columbia istreated as a statistical equivalent of a state for data presentation purposes. (As were American Samoa, the Commonwealth of the Northern MarianaIslands, 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.
Nested Geographies: States
Census Regions and Divisions of the United States
The primary legal divisions of most states are termed ‘‘counties.’’
Counties in 48 States Independent Cities in 4 StatesParishes in LouisianaCities 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: Counties
Census tracts are small, relatively permanent statistical subdivisions of a county or statisticallyequivalent 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 committeeof 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.
Nested Geographies: Census Tracts
Historical Census Geography
Census Tracts– 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
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: Block Groups
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.
Nested Geographies: Blocks
Basic Census Geography
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.
Non-Nested Geographies - Place
Boundary & Annexation Survey
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.
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.
Non-Nested Geographies - CDPs
Historical Census Geography
Places– 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
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.
Non-Nested Geographies – County Subdivisions
Basic Census Geography
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 county-based areas called New England County Metropolitan Areas (NECMAs).
Non-Nested Geographies – CBSA’s
Non-Nested Geographies – CBSA’s
MSAs (366)μSAs (576)
Standalone μSAs (407)
Standalone MSAs (186)
CSAs (125)
PCSAs (718)
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 sub-county 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.
Non-Nested Geographies – Metropolitan Areas
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
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 alarge 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 thelarger 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.
Non-Nested Geographies – Metropolitan Areas
Basic Census Geography
Non-Nested Geographies – Urban AreasUrban 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
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
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/PeriodsPercent in Poverty
Margin of Error: Example, Selected California Geographies/PeriodsPercent in Poverty
1.1. Get the Margin of Error (MOE) from ACS Get the Margin of Error (MOE) from ACS
2. Calculate the Standard Error (SE)2. Calculate the Standard Error (SE) [SE = MOE / 1.645][SE = MOE / 1.645]
3. Solve for Z where A and B are the two 3. Solve for Z where A and B are the two estimatesestimates
22 (SE(B))(SE(A))
BAZ
4. If Z < -1.645 or Z > 1.6454. If Z < -1.645 or Z > 1.645Difference is Significant at 90% confidenceDifference is Significant at 90% confidence
Significance testingSignificance testing
Micro-data Geographies
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
Non-Nested Geographies – PUMAs
Some Key Points to Remember
Census Geographies include nested and non-nested 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
