The investment in Mexico is indeed because it is cheaper to build there, but the other factors are a lot more important than people realize  - The Mexican domestic market is only slightly smaller than Canada's now, having been less than ½ when NAFTA was signed, and should overtake in the next 5 years (vehicle penetration will still be lower than ours at that point).

Net it all out and Mexico probably only a couple of percent above where a share of consumption model would actually put you.

I think we actually run a deficit because of auto parts imported from the US.