Over the past 100 years, the size and composition of the world’s population has been transformed. In 1930, the world was home to 2 billion people; on 21 January 1987 the world marked the birth of its 5 billionth citizen, taking 57 years to add 3 billon people; today (15 November 2022) the world population is estimated to reach 8 billion, taking just 35 years to add the next 3 billion.