As the research guru here at CM, I get asked a lot of questions. Some questions are more complicated than others, but the answers are usually simpler than the methods used to reach the conclusions. For example, how would you explain to somehow how a car starts? The simplest answer is to turn the key, but we all know there is more to it than that. Same goes for research. The answers can be simple, but the explanations are usually much more complicated.
- Ugh, they don’t use zip codes. The census aggregates data at “block group” levels and “census tract” levels, and then at other larger units including counties and states. For many years we cobbled together our own mapping of zip codes to census tracts for local geographic analyses.
- To locate a ZIP code of interest, either use the Find ZIP query or sort on the ZIP code column and then scroll down the table until the ZIP of interest is located. There are 150,806 rows in the table, each showing a unique combination of a census tract (73,057 Census 2010 tracts) and ZIP code area (33,120 Census 2010 ZCTAs).
Enter Research 101. Don’t worry, there won’t be a final exam or even homework. This is simply a blog series I will be writing over the next few months to help answer some of the most common questions surrounding researching methodologies. My goal with this Research 101 series is to provide readers with an educational foundation in market research techniques that can be applied by anyone in the marketing industry.
This month’s post addresses demographics and cartography.
This month’s post addresses demographics and cartography.
One of the most crucial variables in market research is cartographic boundaries. Boundaries are important because data is only as valuable as the area from which it originates. Most of us are already familiar with the most common cartographic boundaries – states, counties, ZIP codes, cities and towns. In the world of research, however, there are other lesser known classification systems used by the Census Bureau for the purpose of providing a stable set of geographic units for the presentation of data. These cartographic systems, in order from smallest to largest, are census blocks, census block groups and census tracts.
First introduced in 1990, census blocks are statistical areas bounded by visible features, such as streets, roads, streams, and railroad tracks, and by non-visible boundaries, such as selected property lines and city, township, school district, and county limits. Generally, census blocks are small in area; for example, a block in a city bounded on all sides by streets. Census blocks nest within all other tabulated census geographic entities and are the smallest unit for all tabulated data. Census blocks in suburban and rural areas may be large, irregular, and bounded by a variety of features. In remote areas, census blocks may encompass hundreds of square miles. As a result, the population of blocks vary from zero to several hundred. In total, there are approximately 8,200,000 blocks in the U.S. and Puerto Rico.
Census Tract Lookup
A census block group is a cluster of census blocks having the same first digit of their four-digit identifying numbers within a census tract. Block groups generally contain between 600 and 3,000 people, with an optimum size of 1,500 people. There are about 39 blocks per census group. Block groups never cross the boundaries of states, counties, or statistically equivalent entities, except for a block group delineated by American Indian tribal authorities. Each census tract contains at least one block group, and block groups are uniquely numbered within the census tract. A block group is the smallest geographical unit for which the census publishes sample data. The United States, including Puerto Rico has 211,267 block groups.
Census tracts are small, relatively permanent statistical subdivisions of a county delineated by local participants as part of the U.S. Census Bureau’s Participant Statistical Areas Program. Census tracts were first used in the 2000 census. Census tracts generally have between 1,500 and 8,000 people, with an optimum size of 4,000 people. Each US county has atlas one census tract. Census tracts are designed to be homogeneous with respect to population characteristics, economic status, and living conditions.
The most appropriate levels of census geographies for linking postal codes are dissemination areas. (DAs), which cover all of Canada, and census tracts (CTs), which occur only in urban areas.note that prior to 2001, DAs were called enumeration areas.
Census tract boundaries generally follow visible and identifiable features. The spatial size of census tracts varies widely depending on the density of settlement. Census tract boundaries are designed with the intention of being maintained over many decades so that statistical comparisons can be made from census to census. However, physical changes in street patterns caused by highway construction and new developments, may require occasional boundary revisions. In addition, census tracts occasionally are split due to population growth or combined as a result of substantial population decline. Census tracts are identified by a four-digit basic number and may have a two-digit numeric suffix. The United States, including Puerto Rico has about 66,000 census tracts.
Census Tract Vs Zip Code Massachusetts
About Census Tract
Census tracts are small, relatively permanent statistical subdivisions of a county or equivalent entity, and are reviewed and updated by local participants prior to each decennial census as part of the Census Bureau's Participant Statistical Areas Program. The Census Bureau updates census tracts in situations where no local participant existed or where local or tribal governments declined to participate. The primary purpose of census tracts is to provide a stable set of geographic units for the presentation of decennial census data.
Census tracts generally have a population size between 1,200 and 8,000 people with an optimum size of 4,000 people. The spatial size of census tracts varies widely depending on the density of settlement. Census tracts are delineated with the intention of being maintained over a long time so that statistical comparisons can be made from census to census. However, physical changes in street patterns caused by highway construction, new development, and so forth, may require boundary revisions. In addition, census tracts occasionally are split due to population growth, or combined as a result of substantial population decline.
Census tract boundaries generally follow visible and identifiable features. They may follow legal boundaries such as minor civil division (MCD) or incorporated place boundaries in some states and situations to allow for census tract-to-governmental unit relationships where the governmental boundaries tend to remain unchanged between censuses. State and county boundaries always are census tract boundaries in the standard census geographic hierarchy.
In a few rare instances, a census tract may consist of discontiguous areas. These discontiguous areas may occur where the census tracts are coextensive with all or parts of legal entities that are themselves discontiguous.
Census Tract Codes and Numbers - Census tract numbers have up to a 4-digit basic number and may have an optional 2-digit suffix; for example, 1457.02. The census tract numbers (used as names) eliminate any leading zeroes and append a suffix only if required. The 6-character numeric census tract codes, however, include leading zeroes and have an implied decimal point for the suffix. Census tract codes range from 000100 to 998998 and are unique within a county or equivalent area. The Census Bureau reserved the census tract numbering range of 9400 to 9499 for use by American Indian area participants in situations where an American Indian entity crosses county or state lines. The Census Bureau assigned a default census tract code of 000000 to some coastal and Great Lakes water and territorial sea, rather than extend the census tract boundary into the Great Lakes or out to the three-mile limit. By closing off some census tracts along the shoreline or just offshore and assigning the default census tract to the offshore Current water areas, the Census Bureau provides complete census tract coverage of Current water areas in territorial seas and the Great Lakes. Because of updates since 2000, there are census tracts with code 000000 that now contain land. Census tract suffixes may range from .01 to .98.
The Census Bureau uses suffixes to help identify census tract changes for comparison purposes. Local participants have an opportunity to review the existing census tracts before each census. If local participants split a census tract, the split parts usually retain the basic number, but receive different suffixes. In a few counties, local participants request major changes to, and renumbering of, the census tracts. Changes to individual census tract boundaries usually do not result in census tract numbering changes.
Relationship to Other Geographic Entities - Within the standard census geographic hierarchy, census tracts never cross state or county boundaries, but may cross the boundaries of county subdivisions, places, urban areas, voting districts, congressional districts, traffic analysis districts, traffic analysis zones, and American Indian, Alaska Native, and Native Hawaiian areas.
Census Tract Numbers and Codes
> 0001 to 9989 - Basic number range for census tracts
> 0000 - Default basic number for census tracts
> 01 to 98 - Suffix codes for census tracts
> 00 - Suffix code for census tracts without a suffix ;
Census tracts generally have a population size between 1,200 and 8,000 people with an optimum size of 4,000 people. The spatial size of census tracts varies widely depending on the density of settlement. Census tracts are delineated with the intention of being maintained over a long time so that statistical comparisons can be made from census to census. However, physical changes in street patterns caused by highway construction, new development, and so forth, may require boundary revisions. In addition, census tracts occasionally are split due to population growth, or combined as a result of substantial population decline.
Census tract boundaries generally follow visible and identifiable features. They may follow legal boundaries such as minor civil division (MCD) or incorporated place boundaries in some states and situations to allow for census tract-to-governmental unit relationships where the governmental boundaries tend to remain unchanged between censuses. State and county boundaries always are census tract boundaries in the standard census geographic hierarchy.
In a few rare instances, a census tract may consist of discontiguous areas. These discontiguous areas may occur where the census tracts are coextensive with all or parts of legal entities that are themselves discontiguous.
Census Tract Codes and Numbers - Census tract numbers have up to a 4-digit basic number and may have an optional 2-digit suffix; for example, 1457.02. The census tract numbers (used as names) eliminate any leading zeroes and append a suffix only if required. The 6-character numeric census tract codes, however, include leading zeroes and have an implied decimal point for the suffix. Census tract codes range from 000100 to 998998 and are unique within a county or equivalent area. The Census Bureau reserved the census tract numbering range of 9400 to 9499 for use by American Indian area participants in situations where an American Indian entity crosses county or state lines. The Census Bureau assigned a default census tract code of 000000 to some coastal and Great Lakes water and territorial sea, rather than extend the census tract boundary into the Great Lakes or out to the three-mile limit. By closing off some census tracts along the shoreline or just offshore and assigning the default census tract to the offshore Current water areas, the Census Bureau provides complete census tract coverage of Current water areas in territorial seas and the Great Lakes. Because of updates since 2000, there are census tracts with code 000000 that now contain land. Census tract suffixes may range from .01 to .98.
The Census Bureau uses suffixes to help identify census tract changes for comparison purposes. Local participants have an opportunity to review the existing census tracts before each census. If local participants split a census tract, the split parts usually retain the basic number, but receive different suffixes. In a few counties, local participants request major changes to, and renumbering of, the census tracts. Changes to individual census tract boundaries usually do not result in census tract numbering changes.
Relationship to Other Geographic Entities - Within the standard census geographic hierarchy, census tracts never cross state or county boundaries, but may cross the boundaries of county subdivisions, places, urban areas, voting districts, congressional districts, traffic analysis districts, traffic analysis zones, and American Indian, Alaska Native, and Native Hawaiian areas.
Census Tract Numbers and Codes
> 0001 to 9989 - Basic number range for census tracts
> 0000 - Default basic number for census tracts
> 01 to 98 - Suffix codes for census tracts
> 00 - Suffix code for census tracts without a suffix ;
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