Phumzile Mlambo-Ngcuka, UN Women Executive Director

Twenty years ago in Beijing, the UN rolled out its Platform for Action, an initiative that sought to empower women worldwide. Yet Hillary Clinton has said gender equality "remains the great unfinished business of the 21st century". So as we mark International Women's Day in 2015, where exactly do we stand 20 years later? Annette Young speaks to the head of UN Women,Phumzile Mlambo-Ngcuka.