Just stumbled on this cool tidbit from ieee spectrum.  Not sure how reliable these numbers are (what metric is used to classify something as a robot?), but its neat to see anyway:

There are now 1 million industrial robots toiling around the world, and Japan is where they’re the thickest on the ground. It has 295 of these electromechanical marvels for every 10 000 manufacturing workers—a robot density almost 10 times the world average and nearly twice that of Singapore (169), South Korea (164), and Germany (163).