The argument on the scale of tax evasion is vibrant. I have contributed figures for the UK and EU. I have in the past contributed to research on losses to developing countries. I think such figures help. The OECD is not endorsing any today. They do not need to do so: I am happy that the loss to the world that I have estimated of $3.1 trillion is indication enough of the seriousness of the issue.
Tax evasion does not, of course, whatever Ritchie says, cost the world anything. We are still a closed system. That less money goes to governments does not mean that that money ceases to exist. It still gets spent or invested somewhere or other.
Indeed, dependent upon what happens to that money, and how badly the government that didn’t get it would have spent it, tax evasion could, conceivably, result in an improvement in the human condition. But even leaving aside such an extreme (for example, someone takes the loot from tax evasion and invests it in a malaria vaccine, as opposed to the British Government which would have used £10 billion to build an NHS computer system that does nothing at all) it’s still true that tax evasion does not mean a loss for the world. Only a different distribution of the cash.