I have had an email from an informed source saying:

I am not sure I share your dismay at the "negligible" assessment of the economic impact of the Government's bill.  My reading of that is that they are saying that the impact on the real economy will be negligible.  The bill is about reducing avoidance (albeit I agree with you that it doesn't go far enough in doing so), which by definition is not something that contributes to the real economy.  I strongly suspect that the HMRC/Treasury policy people who contributed that to the consultation process were well meaning in doing so, and almost certainly did so in order to try to head off the inevitable nonsense from the usual suspects about how the GAAR (weak as it is) will be a disaster for British business.

I think you can tell that the source is sympathetic, and the point made is taken seriously. It bis possible that those undertaking the economic impact assessment of the government's GAAR did use the criteria my commentator notes. But, at the same time the government has been trumpeting that they have reduced avoidance by £500 million. My point is a simple one: if that's measurable and exciting then it must also be possible that they could forecast the impact of their GAAR.

I think they have.

I genuinely think it will have no impact.

And I think there is good reason for that: they intend that it should have no impact. Nothing else can explain how ineffectively it's been designed.