Dr. Eddie Casey:

We do not adjust for the base year. The reason we took those years as starting points for all these simulated receipts was there was this surge over that time and there was an argument 2014 was lower than the historical average and an argument that 2015 was higher. We started from both points and the excess is somewhere in the middle of this range. One thing we have done is charted and looked at what the economy has done in GNI* terms, which we all as economists agree is the right way to look at the economy. What would it have done if we just look at that and how it has evolved alongside corporation tax receipts? What can be seen up to that point in time was this clear relationship between the two, but since 2014-15 there has been a massive divergence where corporation tax receipts have taken off and the link with the real economy has broken down. There really is a clear sense this is excess in a very real sense of the word and that we cannot explain it by looking at the real economy and what is happening on the ground.