What's the ‘Hourglass Ceiling’ behind the gender pay gap?

On average, Australian women are paid $18,461 less than men per year. The recent report released by the Workplace Gender Equality Agency shows a gender pay gap across every sector in Australia. But what’s behind that yawning gap? Professor Lyndall Strazdins from the Australian National University calls it the “massive unresolved problem of our time”. It’s been dubbed the ‘Hour-Glass Ceiling’. So what is it exactly and how can we make men work more like women to fix it?