As it's said on the accordant page:
"They are based on the two-letter country code of the IANA IP address registry of the address from which the work was submitted and could be slightly off."
Some countries indeed seem to do more than they are credited on that page, but I'm not sure if it's better to let the members decide, as everybody would have to do it.
Though an advantage would be that you can work abroad and still the country you're from get's credited.
Maybe a solution already mentioned is best:
Take IANA, unless there's a country entered in the user profile.