Note: ZIP to Congressional District and Congressional District to ZIP Crosswalk Files are now available
USPS ZIP Code Crosswalk files are now available for 2010 Census geographies level beginning with the first quarter of 2012. HUD is not supplying USPS ZIP Code Crosswalks for 2000 Census geographies beyond the fourth quarter of 2011.
One of the many challenges that social science researchers and practitioners face is the difficulty of relating United States Postal Service (USPS) ZIP codes to Census Bureau geographies. There are valuable data available only at the ZIP code level that, when combined with demographic data tabulated at various Census geography levels, could open up new avenues of exploration.
While some acceptable methods of combining ZIP codes and Census geography exist, they have limitations. To provide additional avenues for merging these data, PD&R has released the HUD-USPS Crosswalk Files. These unique files are derived from data in the quarterly USPS Vacancy Data. They originate directly from the USPS; are updated quarterly, making them highly responsive to changes in ZIP code configurations; and reflect the locations of both business and residential addresses. The latter feature is of particular interest to housing researchers because many of the phenomena that they study are based on housing unit or address. By using an allocation method based on residential addresses rather than by area or by population, analysts can take into account not only the spatial distribution of population, but also the spatial distribution of residences. This enables a slightly more nuanced approach to allocating data between disparate geographies.
| How to Read the HUD-USPS ZIP Crosswalk Files: |
There are six types of crosswalk files available for download. The first 3 crosswalk files are used to allocate ZIP codes to Census tracts, counties or Core Based Statistical Areas (CBSA). The last three are used to allocate Census tracts, counties or Core Based Statistical Areas to ZIP codes. It is important to note that the relationship between the two types of crosswalk files is not a perfectly inverse one. That is to say, you cannot use the ZIP to Tract crosswalk to allocate Census tract data to the ZIP code level. For that you would have to use the Tract to ZIP crosswalk file.
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Note: USPS ZIP Code Crosswalk files are now available for 2010 Census geographies level beginning with the first quarter of 2012. HUD is not supplying USPS ZIP Code Crosswalks for 2000 Census geographies beyond the fourth quarter of 2011. |
Allocating ZIP Codes to Census tracts, Counties, or CBSA
The address ratios in 3 files listed below can be used to allocate data from the ZIP code to Census tracts, counties, or Core Based Statistical Areas (CBSA). In these files the denominators used to calculate the address ratios are the ZIP code totals. All three files share an identical structure with the exception of the geographic codes in the second column, which differs between the three crosswalk files – tract, county, and CBSA – respectively.
- ZIP - Tract
- ZIP - County
- ZIP - CBSA
When a ZIP is split by any of the other geographies, that ZIP code is duplicated in the crosswalk file. In the example below, ZIP code 03870 is split by two different Census tracts, 33015066000 and 33015071000, which appear in the tract column. The ratio of residential addresses in the first ZIP-Tract record to the total number of residential addresses in the ZIP code is .0042 (.42%). The remaining residential addresses in that ZIP (99.58%) fall into the second ZIP-Tract record. So, for example, if one wanted to allocate data from ZIP code 03870 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 1.00 (or 100%) due to rounding issues.
| ZIP | TRACT | RES_RATIO | BUS_RATIO | OTH_RATIO | TOT_RATIO |
| 03870 | 33015066000 | 0.0042 | 0.0000 | 0.0000 | 0.0039 |
| 03870 | 33015071000 | 0.9958 | 1.0000 | 1.0000 | 0.9961 |
| ZIP | 5 digit USPS ZIP code |
| TRACT | 11 digit unique 2000 Census tract code consisting of state + county + tract code. The decimal is implied and leading and trailing zeros have been preserved. |
| COUNTY | 5 digit unique 2000 Census county code consisting of state + county. |
| CBSA | 5 digit CBSA code for Micropolitan and Metropolitan Areas as defined by OMB in February of 2013. ZIP codes with a CBSA code of ‘99999’ are not located within a CBSA. |
| RES_RATIO | The ratio of residential addresses in the ZIP – Tract, County, or CBSA part to the total number of residential addresses in the entire ZIP. |
| BUS_RATIO | The ratio of business addresses in the ZIP – Tract, County, or CBSA part to the total number of business addresses in the entire ZIP. |
| OTH_RATIO | The ratio of other addresses in the ZIP – Tract, County, or CBSA part to the total number of other addresses in the entire ZIP. |
| TOTAL_RATIO | The ratio of all addresses in the ZIP – Tract, County, or CBSA part to the total number of all types of addresses in the entire ZIP. |
Allocating Census tracts, Counties or CBSA to ZIP Codes
The address ratios in 3 files listed below can be used to allocate data from Census tracts, counties, or Core Based Statistical Areas (CBSA) to ZIP codes. 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.
- Tract - ZIP
- County - ZIP
- CBSA - ZIP
When a Census tract, county or CBSA is split by a ZIP code, that tract, county or CBSA code is duplicated in the crosswalk file. In the example below tract 01001020200 is split by two different ZIP codes, 36008 and 36067, 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 .0272 (2.72%). The remaining residential addresses in that tract (97.28%) fall into the second tract-ZIP record. So, for example, if one wanted to allocate data from Census tract 01001020200 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. Note that the sum of each ratio column for each distinct ZIP code may not always equal 1.00 (or 100%) due to rounding issues.
| TRACT | ZIP | RES_RATIO | BUS_RATIO | OTH_RATIO | TOT_RATIO |
| 01001020200 | 36008 | 0.0272 | 0.0034 | 0.0278 | 0.0217 |
| 01001020200 | 36067 | 0.9728 | 0.9966 | 0.9722 | 0.9783 |
| TRACT | 11 digit unique 2000 Census tract code consisting of state + county + tract code. The decimal is implied and leading and trailing zeros have been preserved. |
| COUNTY | 5 digit unique 2000 Census county code consisting of state + county. |
| CBSA | 5 digit CBSA code for Micropolitan and Metropolitan Areas as defined by OMB in February of 2013. ZIP codes with a CBSA code of ‘99999’ are not located within a CBSA. |
| ZIP | 5 digit USPS ZIP code |
| RES_RATIO | The ratio of residential addresses in the Tract, County, or CBSA-ZIP part to the total number of residential addresses in the entire Tract, County, or CBSA. |
| BUS_RATIO | The ratio of business addresses in the Tract, County, or CBSA-ZIP part to the total number of business addresses in the entire Tract, County, or CBSA. |
| OTH_RATIO | The ratio of other addresses in the Tract, County, or CBSA-ZIP part to the total number of other addresses in the entire Tract, County, or CBSA. |
| TOTAL_RATIO | The ratio of all addresses in the Tract, County, or CBSA-ZIP part to the total number of all types of addresses in the entire Tract, County, or CBSA. |
A Note about Geocoding
HUD is unable to geocode a small number of records that we receive from the USPS. As a result, there may be some 5-digit USPS ZIP codes that will not be included in these crosswalk files. Less than 1% of the total number of active 5-digit ZIP codes in the country are excluded from the current version of the crosswalk files. 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.
Questions regarding these crosswalk files can be directed to Robert Renner with the subject line HUD-Crosswalks.