Professor Michael McMahon:

There are a number of different ways it can be done. We can go back to before some of the changes in the international tax environment that led to the parking of intellectual property in Ireland and, therefore, the paying of taxes on that, took place and see what was a normal amount of corporation tax paid for a given state of the economy. Then we can extrapolate that out to where we are now with the domestic economy and say if we looked like we did back then or if we looked like other OECD economies and how they get corporation tax, adjusting for different rates, what would be a normal amount of tax for the economy where it is now. That will give an amount and then one can see what we actually took in. The difference between those is what we call "excess". I would like to ask Dr. Casey to come in. There are six different models. He may want to talk the Deputy through all of them or she might ask him to not talk.