When it happens collectively e.g. through taxes, you get somewhat of a middle ground between the survey and giving your own money (directly and visibly). There

When it happens collectively e.g. through taxes, you get somewhat of a middle ground between the survey and giving your own money (directly and visibly). There seems to be some kind of international target of 0.7% of GNI (~GDP) for developmental aid already, which governments often don't meet fully but come close to (e.g. https://commonslibrary.parliament.uk/research-briefings/sn03714/ https://commonslibrary.parliament.uk/research-briefings/sn03...), so the 0.5% would probably be viable in tax form.