Tim Harford tells the fascinating stories of inventions, ideas and innovations which have helped create the economic world.
http://www.bbc.co.uk/programmes/p04b1g3c
Glasses
Spectacles have been around for centuries, and have a huge impact on many people's quality of life. So why is it estimated that more than two billion people aren't aware that they need them? Tim Harford considers the difference that seeing clearly makes to the world.