It doesn't even work (perfectly) within the USA. Zip codes are so unreliable that they're not even used by other government agencies/projects - take a look at t

It doesn't even work (perfectly) within the USA. Zip codes are so unreliable that they're not even used by other government agencies/projects - take a look at the Census, which uses ZCTAs: http://en.wikipedia.org/wiki/ZIP_Code_Tabulation_Area http://en.wikipedia.org/wiki/ZIP_Code_Tabulation_Area The reason for this is that the USPS can change the zip codes without warning (and furthermore, leaves some areas undefined), whereas the Census needs reliable boundaries and fixed geographic areas.