The sun is shining in Los Angeles as Eugene Fama, 79, opens FaceTime for an early morning video interview over the crackly WiFi connection of his holiday home. He is on the West Coast with his wife, Sallyann, escaping the chilly winter in Chicago, where he has lived and worked for almost 50 years.

His Nobel Prize-winning efficient markets hypothesis, which shows markets are unpredictable and so, Fama argues, it is a waste of time (and fees) trying to beat them, changed the world of finance. It is a key driver of what has become an explosion of passive investment vehicles, now estimated to be worth $5.3tn.