Every few years, the Organisation for Economic Development (OECD) assesses the mathematics level of hundreds of thousands of students around the world. In 2000, when the first tests were held, Australia ranked 6th for maths. In the most recent results, we had dropped to 19th. Here's why we need to be literate in maths, and why our failure to do so is spelling bad news for our careers, life choices -- and even our mental health.