It has always been entertaining to read predictions that fail the test of time. In 1865, as engineers were racing to develop the telephone, an American editor sniffed: “Well-informed people know that it is impossible to transmit the human voice over wires?.?.?.?and that, were it possible to do so, the thing would be of no practical value.”A more recent favourite is the 2007 interview with Steve Ballmer, then chief executive of Microsoft, in which he confidently declared: “There’s no chance that the iPhone is going to get any significant market share. No chance.” About one in five smartphones sold globally is now an iPhone.

Fun to gloat, perhaps, but less entertaining to have money resting on your own predictions. Unfortunately, investing requires you to do just that. You cannot avoid having to make forecasts. If you own a share today then you must believe that it will be worth more in future.

Maybe you think the company has a product that will enjoy growing sales. Maybe you think the share price does not reflect current profits. Maybe you believe you are on to something early and that you will offload your stock once the herd belatedly piles in.