The world's population is due to hit 7bn this October.
If today the world's population is (almost!) 7 billion, what was the population when you were born? How much has the world's population changed in your lifetime? This interactive link shows the acceleration of growth powerfully (disclaimer: the dataset only works on dates after 1951--hint: if it was before 1952, world population was smaller than 2.5 billion).
Via Seth Dixon