We're almost a quarter of the way into the 21st Century and already it's clear money has changed. 

It's increasingly mobile. It's (relatively) cheap and more and more digital. Economist Richard Holden is charting the changes. 

Guest: Richard Holden, Professor of Economics at the University of NSW Business School

Author of "Money in the 21st Century; Cheap, Mobile, and Digital' published by University of California Press.