This will be a discomforting, defining week for the global economy. That is not because the US Federal Reserve is set to cut interest rates. Rather it is because of the strikingly low level of rates from which the Fed will start: a range of just 2.25 to 2.5 per cent.

After more than a decade of economic expansion, and despite everything from tariffs to tax cuts, it seems this is as high as US interest rates go. Meanwhile, the European Central Bank is debating whether to reduce its negative rate still further. Until this month, it was possible to imagine that pre-financial crisis levels of 4 to 5 per cent might eventually return. No longer.

According to their own projections, Fed officials believe rates will settle at 2.5 per cent in the long run. Subtract their 2 per cent inflation target and the real reward for capital is going to be a miserable 0.5 per cent. The equivalent rate in Europe and Japan will almost certainly be much lower. Such low levels of interest rates are a profound change from the past. (The federal funds rate was 6.5 per cent, and the real rate was about 4 per cent as recently as 2000.) Although interest rates touch almost every aspect of economic life, the developed world remains deep in denial about the consequences. Here are eight themes for investors and policymakers to ponder.