In 2014 it was in terms of revenue (all euros)
EU - 122.86B
Asia Pacific - 38.11B
North America - 27.62B
South America - 13.87B
(source statista.com)
so that's about 13.7% (but includes Mexico and Canada as well as the US I assume). I would guess (?) that these are reasonably indicative of assets, possibly biased in exaggerating the USA contribution given their major manufacturing bases?
Biting the hand that feeds IT
