How does MIG create Zip Code data?

MIG produces data files at the National, state and county level for use with IMPLAN software. MIG also can make sub-county level files - at the zip code level. By specifying zip codes it is possible to create a city, a watershed , or any subset of a county or counties. Note: Zip codes do not necessarily follow political boundaries or desired physical boundaries - these inaccuracies of boundary description; however, may be more desirable than using county boundaries -if not, the county files are cheaper, so use them. Our main source of data, for generating zip code files, come from the County Business Patterns (CBP) program. They release 4-digit SIC employment data at the zip code level. The data; however, do not consist of employment counts but rather 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 4-digit SIC sector. 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 by the number of firms in that size class. By adding the products (of the multiplications) for a single sector we create an estimate of the employment for that sector. Given a set of zip codes for a desired region we ca add together the employment estimates based on CBP data. We also add together employment data for the zip codes for the county(ies) which contain the desired region's zip codes. After aggregating the 4-digit SIC data to the 528 IMPLAN sectors we can create ratios for distributing the county(ies) level IMPLAN data file to the desired zip-code region.