[mzs]

Slight correction, EPA was not slow to act. When they caught wind of this they approached VW who had one excuse after another:

http://www.washingtonpost.com/news/wonkblog/wp/2015/09/22/an...

[qubex]

The EMH predicts that unless the net probability of effects where totally zero there would be a move. I don't see evidence of there having been one.