In 2014, global output per head grew by close to 2 per cent, at purchasing power parity. Thus, at the end of the year, human beings were, on average, better off than ever before in their long history. This is also likely to be true at the end of 2015. Optimism is sensible.

Indeed, it is easy to imagine a far better performance in 2015 than in 2014. The most important reason is the collapse in oil prices, particularly since these higher prices are in large part due to enhanced supply. The International Monetary Fund argues that lower oil prices could raise world output by between 0.3 and 0.7 per cent in 2015.

With its healing from the financial crisis largely complete, the US economy looks particularly strong. The Federal Reserve may raise rates a little in 2015, but not much. With the federal budget deficit expected to be below 3 per cent of gross domestic product, further fiscal tightening is unneeded. Long-term interest rates on 10-year treasuries remain close to 2.2 per cent. In all, the opportunity for an acceleration in growth looks very good.