Stuart Russell:

Industry [has probably invested] more in the last 5 years than governments have invested since the beginning of the field [in the 1950s].

My guess is that Russell doesn’t have a source for this, and this is just his guess based on his history in the field and his knowledge of what’s been happening lately. But it might very well be true; I’m not sure.

Also see How Big is the Field of Artificial Intelligence?