At the time , the world population stood at 5.5 billion , and optimistic scenarios predicted a peak of 7.8 billion by 2050 , a number that current estimates show will be reached around 2030 . At the time , the world population stood at 5.5 billion , and low-bound scenarios predicted a peak of 7.8 billion by 2050 , a number that current estimates show will be reached around 2022 .