Shifting is meant to be taken in a very general sense. It should include the efforts to change tax laws, to exploit loopholes in the international tax system, and so on.

And, in similar vein, determining how much value one created is again a general problem.

Economics is full of these problems, where the theorem/definition/principle is easy to state, but hard to compute. That said, it's not impossible to estimate these things and use those to guide policy.