I am a foreigner who works for an American customer and I freely admit that I am not as productive as one of their in-house developers. This is because of things like communication delays, lack of documentation (of both their code and their business logic and practices) and generally the overhead of being in a separate team.

Now that IBM has more people in India than in the US, maybe they will find that they face the opposite problem: US workers will have to adapt to their Indian counterparts instead of the other way around, so it will be more productive to hire an additional Indian than an additional American.