We only create data for those zip codes for which we have one of the following: land area from the latest Decennial Census, population or household count (by income group) from the latest American Community Survey (ACS), railroad employment from the latest Railroad Retirement Board report, or Census County Business Pattern (CBP) employment. Having at least one of those allows us to distribute part of the county's data to the zip code.
It should be noted that after getting the raw data for all of our geographies, we also balance population estimates prior to writing final IMPLAN data. Basically, we make sure that zip codes add up to counties, counties add up to the states, etc. As a result of this balancing, numbers won't be 100% comparable with raw data, even if we were comparing to the exact same tables that the data team started out with.
Census CBP Data
The CBP program publishes 6-digit NAICs employment data at the zip code level. Rather than employment counts, the CBP data provides information on the number of firms in each of 14 firm size classes (e.g., 1-4 employees, 4-9 employees, 10-19 employees, etc.) for each 6-digit NAICs industry. This allows the CBP to avoid disclosing the exact number of employees at a single firm.
We take the mid-point of each of the size classes and multiply this by the number of firms in that size class (e.g. if there are 6 firms reporting under a single NAICS code for 4-9 employees, we get an estimate of ~39 employees for that NAICS code and class). By summing the estimated number of employees within a 6-digit NAICS specification, and aggregating the NAICS code employment values into their appropriate IMPLAN industry, we create an estimate of the employment for that industry at a zip code level. We also add together employment data for the all zip codes represented in a larger region (county or counties) to aid in distribution of non-employment IMPLAN data to individual zip code regions.
After aggregating the 6-digit NAICs data to the IMPLAN sectoring scheme, we can create ratios for distributing the county-level IMPLAN data to the zip-codes that belong to each county. The ratio is derived by dividing the specified zip-code's employment in that industry by the sum of all the county's zip-codes' employment in that industry.
Employment ratios are used to distribute all industry data (Employment, Output, Employee Compensation, Proprietor Income, Other Property Type Income and Tax on Production and Imports) into their respective zip code regions.
Proxies are used to distribute industry sectors that CBP does not cover to ZIP Code regions. These sectors, and the proxies used to separate the zip code employment from the county(ies) are shown below:
- Agricultural Industries: These are estimated from current Census of Agriculture- county level farming is distributed to zip codes based on the Census number of farms by zip code.
- Railroad: These are estimated based on trucking and warehousing distribution employment as a proxy.
- Religious organizations: Population is used as the proxy for determining these employment values.
- Government, except education: Total employment for the zip code is used to distribute county level government employment.
- State & local education: Population is used.
- Construction: Employment for NAICS 22 is used for this proxy.
ACS Population and Household Counts by Income Group
Census population and household count data are also available at the zip code level through the American Community Survey (ACS) program, and are similarly used to create ratios among all the zip codes that belong to a given county, which are then used to distribute the county values for various data points to the zip codes in that county. For example, population ratios are also used to apportion out county-level personal income and institutional sales, while household counts by income group are used to distribute county-level PCE by household income group.
Final Demand Proxies to Distribute Zip Code Regions
Final demands also need to be estimated. Below are listed the proxy values used to distribute the county-level final demands to a zip code area.
- PCE (9 classes): ACS household counts by income group. I.e., if the zip code area has 10% of highest income households it gets 10% of the county's highest income group's PCE final demand.
- Fed Military & Non-military: overall employment
- State & Local Education & non-education: overall employment
- Federal Sales: overall employment
- State & Local Gov Sales: overall employment
- Investment: employment by industry
- Foreign Export: employment by industry
- Change in Inventory: employment by industry
Because of the limitations of the data, productivity data for the zip code area is the same as for the county containing the zip code area. The following examples are included as part of the productivity data:
- Output per Worker
- Earnings per Worker
- Value Added to Output ratio
Updated March 29, 2021