Derived is not a simple proposition for multinationals. The IPad I'm writing this on was assembled in China, sold in Ireland, using code developed in the US, wh

Derived is not a simple proposition for multinationals. The IPad I'm writing this on was assembled in China, sold in Ireland, using code developed in the US, where the rights to that code are held in Ireland (I believe). Each of those countries (and many more I am sure) contributed to the sale. Where was that income derived? Add to that different tax laws in terms of accountability and you have our mess.