Mr Jamie Dimon, the chief executive of JPMorgan Chase, recently had a few things to say about cryptocurrency. Bitcoin, he declared, is a “hyped-up fraud”; it’s a “pet rock”.

Actually, Mr Dimon seems to share the same view of Bitcoin that I and many other economists have had all along: The digital “currency” isn’t really a currency. That is, it can’t be used as a medium of exchange – there are very few things you can buy directly with Bitcoin – and it isn’t a stable store of value with reasonably predictable future purchasing power. So it’s basically useless; as Mr Dimon says, it’s a pet rock.