Poor Thomas Malthus. The 18th-century theorist, who believed that population increases would inevitably be checked, must have turned in his grave when the seven billionth person was born on October 31 this year. (The timing was disputed, but that was mere detail.) The event meant that the world’s population had doubled in just four decades. If present trends continue, it will hit 9bn by 2045/50.

Investors should care about that. Demographics are important over the medium and long term. The tricky bit is trying to translate these trends into anything approaching reliable investment opportunities. In the US, the most successful sectors over the past 40 years have been oil and gas (the index has increased 80-fold) and healthcare (60-fold), according to Datastream. By contrast, international food prices, using the UN FAO index, have merely quadrupled. Would anyone in 1971 really have predicted this, even if they realised – as the US Census Bureau did – that heady population growth was likely for more than 60 years?

Absent Armageddon, some population trends are inevitable and therefore potentially profitable as investments.