So, for example, if one wanted to allocate data from ZIP code to each Census tract located in that ZIP code, one would multiply the number of observations in the ZIP code by the residential ratio for each tract associated with that ZIP code.
Note that the sum of each ratio column for each distinct ZIP code may not always equal 1. The decimal is implied and leading and trailing zeros have been preserved. In these files the denominators used to calculate the address ratios are the totals of each type of address in the tract, county or CBSA.
All three files share an identical structure with the exception of the geographic codes in the first column, which differs between the three crosswalk files — CBSA, County, and Tract — respectively. In the example below tract is split by two different ZIP codes, and , which appear in the ZIP column.
The ratio of residential addresses in the first tract-ZIP record to the total number of residential addresses in the tract is. The remaining residential addresses in that tract So, for example, if one wanted to allocate data from Census tract to the ZIP code level, one would multiply the number of observations in the Census tract by the residential ratio for each ZIP code associated with that Census tract.
Since the HUD geocoding base map is updated regularly, an effort is made to re-geocode these records with every new quarter of data.
As a result, these crosswalk files will be generated on a quarterly basis and may differ slightly from quarter to quarter. We try to publish the Crosswalk Files by the end of the month following the quarter. For example, we aim to publish fourth quarter by the end of January, first quarter by the end of April, and so on. Do ZIP Codes align with political or administrative boundaries? ZIP Codes do not align with political or administrative boundaries. ZIP Codes frequently cross county, city, and town jurisidctions.
ZIP Codes may also potentially cross state borders. For example, Lake County census tract The tables below include lines for each of those external census tracts, but those external census tract numbers are not listed in the Census Tract column see instead the Tract Code column.
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If you continue with this browser, you may see unexpected results. More accurate geographic match -- census tracts are one of the specific geographic units by which census counts are presented; ZIP Code Tabulation Areas are used to approximate the geographic boundaries of ZIP Codes. Better aggregation of geographic boundaries for comparisons with municipal and county data -- Census tracts do not cross county lines and typically break out data for incorporated places.
Less frequent boundary changes -- Census tracts tend to be stable for 10 years or more. Postal Service adjusts to maintain efficient delivery zones.
ZIP codes rarely do because that would require two postal workers delivering mail to that street - one for each side of the street. In the example, one mail carrier may deliver to 3 sides of the block via one ZIP code while another mail carrier delivers mail on the other street in a different ZIP code. When this happens, the Census Bureau will assign the entire block to a single ZCTA in this case, because the census block is the area that is precisely measured.
If you are getting very precise usually a matter of meters, not miles , census block boundaries near the edge of a ZIP code almost always split ZIP codes. The statistics provided by the Census Bureau can give insight into the demographics within the ZIP code. For instance, see our ZIP code rankings. Remember that ZIP codes were made to make mail delivery easier. They weren't made to correspond to existing boundaries such as cities, counties, or even states.
If it is more efficient for a mail carrier to drive across a state line to deliver mail, the ZIP code "boundary" will cross the state lines. ZIP codes don't usually cross state lines, but some do , , and are good examples. The edges of the boundaries commonly overlap. For the purposes of our free zip code database by county downloads, we will commonly list either the most common region for the ZIP code or list multiple regions if several exist in the ZIP code.
For cities, the assignment is somewhat more complicated. The assignment of cities to ZIP codes is more general. The city is usually the name of the main post office. For instance, almost all ZIP codes in St. Louis County in Missouri have a city of Saint Louis when they may be more accurately described as the name of a smaller city where they are located. Click here to learn more about matching ZIPs to cities and counties.
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