In the GWI Core survey, we now ask respondents for their partial postal codes to allow us to code their city, additionally to their regional information. This is available in Australia, Canada, France, Germany, Italy, Spain and the UK.
Methodology
The cities that we include in the platform are selected based on population criteria, aiming at a representation of the 50 most highly populated cities per country. If a respondent belongs to a city that is not included in the total of represented cities, they are coded in an ‘other’ datapoint, that corresponds to their region (e.g. Catalonia (other)).
We collect 3-digit (all countries excluding UK) and 4-digit (UK) postal codes and use a verified postal code source to map each partial postcode to a city and region.
Mapping codes to cities
For the mapping, each partial postal code is assigned to the specific city it corresponds to. On occasions of conflict, when multiple cities are associated with one single partial postcode collected, the decision on their assignment is based on:
Regional data which we still collect in a separate question
Population criteria (selecting the highest in population among the cities the code responds to)
Validation
While creating the cities’ question on the platform, we ensure that:
Every postal code is assigned to only one city
The respondent input corresponds to valid postal codes
There are no conflicting information between the questions included in the platform (regions, cities)