Resolve why MailStream Plus PRFZIPDR DB file always says a 5-digit ZIP CODE is all one county.

MailStream Plus all versions, all platforms


A MailStream Plus (MSP) user questioned that in the PRFZIPDR file, the 5-digit 41537 for example was listed as just being in Letcher county, while the user knew that some addresses in that ZIP Code were actually in Pike county.
ZD41537       JENKINS      KYJENKINS                  204092LETCHER                 N1338041503A      N 41537A
  |||||                                                     |||||||                  |||   
  ZIP                                                       County                   FIPS County code  


The PRFZIPDR file is based on the USPS's City-State file which lists one FIPS code for each.5-digit ZIP Code  It is not intended to be accurate for the actual physical county location for all addresses.  A 5-digit ZIP Code is always listed as being in one county, because that is what MSP uses to look up the USPS facility's FIPS code.

MSP looks up the Entry Point's county FIPS code based on the 5-digit ZIP Code, and uses that value as a match code to determine if a record has the same FIPS value and so is eligible for Periodical In-County rates. 

CODE-1 Plus (C1P) does *not* use the City-State file which is based on just a 5-digit ZIP Code.  C1P returns a more accurate FIPS county code that reflects the actual county the address is in. 
For example, as far as USPS mailings are concerned, for this purpose mailers can consider any address in 41537 as Letcher county (mainly because that is where the USPS facility that delivers to 41537 is located.)


UPDATED: July 31, 2017
No resolution needed.  The DB files used in MailStream Plus (MSP) are per the USPS regulations for mailings and in-county pricing, not for location accuracy.

FYI- The DMM says that some addresses may actually be outside a county, but may be eligible for In-Country rates, because of the way a USPS Carrier Route goes-
DMM 207 
11.3 In-County Prices 
11.3.2 Exceptional Conditions 
d. A publication entered within the county in which it is published, but distributed outside that county on a postal carrier route originating in the county of publication, is treated as if distributed within the county of publication.

That's because some Carrier's routes might extend partially outside of the originating county.

CODE-1 Plus (C1P) does not return the county code that would be needed by MSP if the above exceptional condition applied to any address.
And this is not a defect in C1P either.  It returns what county an address is really in, it's not designed to give the county code if the exceptional condition above applied to an address.  

If the exceptional condition *did* apply to an address, the mailer would have to manually change the FIPS code in the record(s) to have the correct code to get In-County.  It is not sure how that would or even could be determined by a mailer, or even whether the USPS makes data available that would allow a mailer to know.

But in the real world, the exception applies to a very very small percentage of pieces that get a different FIPS code from C1P, that might be eligible for In-County but are *not* getting it.