The world population over the next three centuries : explosion , implosion or equilibrium ?

blished the final version of a bold exercise in population projection: several scenarios of the future of every country in the world to 2300 [1]. According to the study, the world population will continue to grow rapidly until 2075, reaching a historic high of 9.2 billion, compared with 6.4 billion now, and then gradually stabilize at around 9 billion. But this is only the central scenario, based on the assumption that the fertility rate will eventually settle at the replacement level, i.e. 2.1 children per woman. The United Nations demographers also show that by adding or subtracting a few decimal points to this rate (plus or minus 0.5 children per woman on average until 2050, then 0.25 thereafter), the world population would rise to 36.4 billion or fall to 2.3 billion in three centuries’ time. Given this extraordinarily broad range, it is easy to be sceptical about the value of the exercise. Researchers who prefer probabilistic projections, i.e. with clearly defined confidence intervals, are unimpressed [2, 3]. Finding out that there is a 95% chance of the world population being somewhere between 2 billion and 36 billion in 2300 does not tell us much. But, anticipating that criticism, the UN’s demographers assert that the projections are not intended to be forecasts of the future, but extrapolations of current trends with a target. They The world population over the next three centuries: explosion, implosion or equilibrium?