Per person depositing in an institution. On European level, it would be futile to try to limit it to EUR100k per person, for many reasons, for instance because lots of people can have multiple identities -- expect perhaps in the Big Brother societies in the northern EU countries, where you can actually do a census by saying SELECT COUNT(id) FROM population WHERE alive=1;
Moreover, how would you treat accounts that are not owned by a person, but e.g. companies?
Moreover, how would you treat accounts that are not owned by a person, but e.g. companies?