Let's try this - tell me where he could be. He could be in Canada, India, Indonesia, East Africe, East Russia, or West China. We can see all of the other bonuses that don't have wastelands in them, and I think we can agree he probably hasn't had enough income to have broken down wastelands at this point in the game.
Of those, he can't have East Russia, Canada or West China alone and still have 12+ income. And I don't believe he has had enough time to take one of them on his own.
That leaves India/East Africa and India/Indonesia as the two most likely cases, right?
So now the next question is, which pair is most likely. We started out early saying that impaller would probably spread himself out instead of bundling up his eggs in one basket, and I still very much agree with that. So it's more likely that he's in east africa then indonesia. Which is why we send the big F.U. army there this turn and break his biggest bonus and try to demoralize him. His armies are way out of position, we beat him silly.
Of course, that could fail in a lot of ways. He might try to take South Africa himself this turn (which is why it should be our first move, if not an order priority move). He might already have some spare armies up there, so it's not as easy an attack (although he can't have too many since we've seen his income at play). Or he might not be there at all.
But if he's not there, he's in Indonesia. And we're three turns away from the evil fork in Australia, where we can put a big army that borders him, and move it left and right in a single move, while he can't do the same - it takes two moves to move armies from border country to border country. I'd love to find out he wasn't in East Africa. We'd take it ourselves, and start moving on Australia immediately.
Sure, it could backfire a little. But this thing of, maybe if we put all our armies over here, and then we get lucky and move first, and then we hopefully can stop him for at least one turn - it turns out that can backfire much worse than my plan.