The number of Austrian citizens residing abroad is estimated by the Federal Ministry for European and International Affairs on the basis of voluntary registrations of Austrians abroad with the Austrian representation authorities abroad. The results are updated annually for the reference date of 1 June. In addition to the registers of the Austrian representative authorities abroad, in some countries (especially Germany and Switzerland) national data sources can be used to determine the number of registered Austrian citizens. In general, this number is significantly lower because it only counts citizens with a minimum residence period of 12 months and dual nationals are listed with the nationality of the host country.