Geographic Terminology

Block
An area of land bounded by physical, visible features. Most often, the features are streets (roads, highways), railroad tracks or water. Electric power lines, drains and ditches are sometimes used as block boundaries as well. Imaginary municipal boundaries are not used as block boundaries unless they are also census tract boundaries. County lines, real or imaginary, are always block boundaries.

Blocks were identified by three digit numbers in the 1970-1990 period, but will have four digits beginning in 2000. They are numbered within tracts. The second digit will almost always be a zero (0).

Block group
A group of blocks with the same first digit.

Tracts
An area of land bounded by features as described for blocks, or by municipal or county boundaries. Tracts are defined as statistical geography, meaning that they are created for the purpose of presenting data. Tracts are drawn by local statistical areas committees working in cooperation with the Bureau of the Census.

Census tract numbers are four digits and may have two digit suffixes as well. The suffix, if present, is separated from the main number by a decimal point. E.g.: 3508.01

The entire nation has been tracted for the 2000 census. In rural areas, the tracts will resemble the Block Numbering Areas (BNAs) used in 1980 and 1990.

Minor Civil Division (MCD)
In Michigan, a census-defined MCD is a city or a township. MCDs comprehensively cover all the territory within a county, and are also known as county subdivisions.

Local convention, used in SEMCOG and SEMCC publications, defines an MCD as a city, village, or township (subtracting any villages within it).

Place/Census Designated Place (CDP)
In Michigan, cities and villages are places, as well as other areas which may be "census designated places" (CDPs). Townships are not places unless they also have CDP status. Most townships over 25,000 population in Wayne, Oakland and Macomb Counties do have this status. Outside these three counties, most CDPs are small urban agglomerations which have no official political status. An example is Whitmore Lake in Washtenaw and Livingston Counties.

Metropolitan Area (MA)
A Metropolitan Area is a county or group of counties which meet criteria established by the U.S. Office of Management and Budget. As of 2000, there are nine MAs in Michigan, as follows (see below for description of PMSA/CMSA):

PMSA: Ann Arbor (Washtenaw, Livingston & Lenawee Counties)
MSA: Benton Harbor (Berrien County)
PMSA: Detroit (Wayne, Oakland, Macomb, Monroe, Lapeer & St. Clair Counties)
PMSA: Flint (Genesee County)
MSA: Grand Rapids (Kent, Ottawa, Muskegon & Allegan Counties)
MSA: Jackson (Jackson County)
MSA: Kalamazoo-Battle Creek (Kalamazoo, Calhoun & Van Buren Counties)
MSA: Lansing (Ingham, Clinton & Eaton Counties)
MSA: Saginaw-Bay City-Midland (Saginaw, Bay & Midland Counties)

PMSA/CMSA
A metropolitan area of more than 1 million population may be organized into two or more Primary Metropolitan Statistical Areas (PMSAs). When this happens, the PMSAs together are defined as a Consolidated Metropolitan Statistical Area (CMSA). In Michigan, the Detroit-Ann Arbor-Flint CMSA, a ten county area, is divided into three PMSAs as outlined above.

CBSAs and Combined Areas -
The metropolitan area concept has been significantly revised for use after the 2000 census. The term for the areas will switch to CBSA, which stands for Core-Based Statistical Area. The definition of areas will go down to cores of 10,000 population, with the areas between 10,000 and 50,000 being referred to as "micropolitan" areas. It also appears likely that the primary CBSA unit will be like the PMSAs of 1980 and 1990, while some adjoining CBSAs will be combined under certain conditions. Michigan will add about a dozen micropolitan areas under this new definition.

The new definitions will be promulgated in late 2002 or early 2003.

Metropolitan County
A metropolitan county is a county that is part of a metropolitan area (MA/PMSA/CMSA). Metro county status is important in Medicare reimbursement funding and some other programs. Metro counties usually have census tracts. Michigan has five counties which were once part of metropolitan areas but are no longer: Barry, Ionia, Oceana, Shiawassee and Van Buren.

Urbanized Area (UA)
An urbanized area is an agglomeration of at least 50,000 population living at a density of at least 1,000 persons per square mile. UA boundaries are defined at the block level and do not cover entire counties. They are important for transportation funding.

Urban Clusters
Urban clusters are defined in the same manner as urbanized areas, but are between 2,500 and 50,000 population.

Urban/rural
Prior to 2000, "urban" meant any territory in an urbanized area, in an incorporated place of 2,500 population or more, or in a census designated place (CDP) or 2,500 population or more. What wasn't "urban" was designated "rural." Subsequent to the 2000 census, and using the 2000 census urbanized area criteria, "urban" is any territory in an urbanized area or an urban cluster. This means that unincorporated territory around smaller cities and villages (under 50,000) will now be urban, while very small cities will not be urban unless they meet the urban cluster criteria. For more information about urban/rural definitions, see www.census.gov .

ZIP Codes and ZCTAs
The ZIP code, an administrative geographic area created by the Postal Service, is the most well known geocode.

ZIP Code Tabulation Areas (ZCTAs) are close approximations of ZIP codes, rounded to whole census blocks. For practical purposes, ZCTA tabulations can be used to represent data for ZIP codes in almost all instances.