Who first thought of putting wheels on suitcases and why did this seemingly obvious idea not take off until the 1990s? In the final episode of our series on how innovation works, we explore how the adoption of an idea can be hampered by social attitudes and prejudices. In the case of the wheeled suitcase, it wasn’t a change in technology that made the difference—instead, the crucial change took place inside people’s heads. Tom Standage hosts. For full access to The Economist’s print, digital and audio editions subscribe at economist.com/podcastoffer   See acast.com/privacy for privacy and opt-out information.