Nor is clamping down on the black economy such a big deal. Admittedly these things are hard to measure, but according to research by the London School of Economics, the black economy only accounts for 10pc of British GDP, which is the fourth lowest in the EU. Many of the people working in it are below the tax threshold anyway, and certainly below the VAT threshold. So the tax collected even if you clamped down completely is unlikely to amount to more than 1pc of GDP. As for negative interest rates, do we really want those? Or have we concluded that central bankers are doing more harm than good with their attempts to manipulate the economy?