Sometimes a species reaches the end of its natural existence. As its numbers dwindle, disappearance becomes inevitable and the last survivors of the doomed herd become objects of curiosity and pity. This is happening to chief executives who are also chairmen — but with none of the pity.

It is a slow process. Well over half of S&P 500 companies do not yet have independent chairs. Plenty of chief executives are also chairman. A few, like beribboned African potentates awarding themselves more medals, also add “president” to their honours.

But around the world, the arithmetic is against title-hogging corporate leaders. Where they exist, they are simply not being replaced. Strategy&, the consultancy, says only one in 10 companies awarded joint titles to incoming chief executives in 2014, near an all-time low. As recently as 2002, more than half of incoming chief executives in Europe and the US held both titles.