In 1968 John Brunner, a British novelist, worked out that the entire world’s population of 3.5 billion could stand shoulder to should on an island the size of the Isle of Man (572 km²). In 1950 the earth’s 2.5 billion people could have squeezed on to the Isle of Wight (381 km²). He prophesised that by 2010 there would be 7 billion people, and they would fit on an island the size of Zanzibar (1,554 km²).
The result was his novel Stand on Zanzibar which centred on the consequences of overpopulation. His societal predictions were not fulfilled, but he was only a year out in workingout when the earth would welcome number 7,000,000,000.