We do not need to store the area of a surface, as it can be calculated. Nevertheless, there are keys such as area_ha or area_sqkm that can be used instead of the foreign key UArea. Please do not use the key area, as it is a pure Boolean value (yes/no). For the population, there is the key population, and for the date of recording, there is population:date. Please note the OSM notation for the date here.
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