World leaders had been planning for a world population of about 9 billion by 2050. But now a new analysis, based on fresh data and more advanced statistical methods, suggests that this estimate might be wildly inaccurate and that the real figure might be more than 12 billion, which means population policy might need a major rethink. Adrian Raftery at the University of Washington is the author of the new study... Like this podcast? Please help us by supporting the Naked Scientists