He’s missed what we mean by markets being efficient:
If markets are to be efficient in the way that economists have described — and as those who suggest they provide optimal solutions profess to believe they operate — then there must be the highest-quality information available to all market participants so that they can act rationally, allocating resources to the person who is best able to use them to maximize return, and who exposes the provider of capital to the lowest risk in that process. Very obviously, tax havens undermine these principles. They are in fact designed to deny market participants the information they need to act rationally, allocate resources efficiently and minimize risk. … If risk is increased, then the required rate of return within marketplaces also increases. This means that the number of projects that can be invested in is reduced, so that the amount of capital committed is diminished. As a consequence, productivity declines, and along with it growth, output, wages and profits
But that’s not what we mean by market efficiency. Rather, we mean that markets are efficient at processing information. It’s entirely opposite. It’s not that markets are efficient thus we must make sure markets have lots of information. It’s that because markets are efficient everything that people know will be efficiently incorporated into prices.
For people trade on what they know. Thus some people knowing something means they trade, that knowledge is then in post-trade prices.
He’s simply got the idea of efficiency entirely the wrong way around.