Have you ever really thought about what it is that creates the modern economy? These are the things that surround us and we interact with, or depend on, everyday but rarely think about. From credit cards, to shipping containers, batteries and double-entry book-keeping, there are a lot of things that are more interesting than you may think. And for this special Christmas edition of the This is Money podcast we have a treat for you. Tim Harford, author of Fifty Things that Made the Modern Economy, presenter of the podcast of the same name, and Undercover Economist makes a guest appearance. He joins Simon Lambert, Rachel Rickard Straus and Georgie Frost in the studio to talk about what it is that shapes the world around us, why it matters, and how what are commonplace things now were dreamed up and then completely changed the way we live.