GIA Consistency (Or Lack Thereof)?

[Beckywecky]

Is GIA consistent across all their labs? I'm told that GIA in India has a somewhat looser standard than its USA conterpart. Of course, as consumers we have no way of knowing where the stone was actually graded, correct? Thoughts? Insight? The reason I'm asking is there does seem to be a lot of varaition, especially in the SI1 - VS range.