Every year, tens of thousands of aspiring young moguls enrol at business school for an MBA, hoping to climb the corporate hierarchy. They are following predecessors who now run many leading companies, from Alphabet, Amazon and Apple to Microsoft and Walmart.And the aim of faculty and administrators remains what Harvard Business School’s first dean, Edwin Gay, expressed in 1908: “To train people to make a decent profit, decently”.

Better knowledge and training can make leaders more innovative and productive, raising the returns to all stakeholders. Better managed businesses can more effectively achieve whatever objectives they set, including helping to tackle the myriad challenges society faces.

But has the MBA actually achieved these goals? Our recent research suggests a much less encouraging picture. Using detailed data on companies and workers from the US and Denmark, we looked at the effects when a chief executive with an MBA or undergraduate business degree takes over from one without such qualifications.