The U.K. government has spent a lot more money trying to discredit my number than it's ever invested in actually trying to get the number right, and that's an unfortunate use of funds.
There is a fundamentally different approach between the two of us. They take the tax returns they receive and try to calculate the error rate within them. I actually look at the total economy and the level of activity within it, and then look at the total recorded level, which is fundamentally working from a GST level and saying that if GST is going to be avoided—it's VAT here, but GST in your terms. If the VAT is being evaded, then actually the income tax, the payroll taxes, the profit taxes, and everything else will be lost, because GST is on the top line of the profit and loss account.
I'm an accountant, so I do what's called a top-down approach; they do a bottom-up approach. Their approach has to be flawed because they don't include all the people who fail to send in their tax return in the first place; therefore, their number is bound to be smaller than mine. Somebody who completely skips the system isn't in their estimate. So they have it wrong.
The Financial Times in the U.K. called those numbers completely made up, and I would tend to agree with that analysis. We have to be more sophisticated than they are, but we also have to be aware that we are not estimating, and that's as good as we'll ever get.