The governor of the Bank of England, Mark Carney, recently argued that more thought should be given to creating a global electronic currency. This column, part of the Vox debate on the future of digital money, looks at the challenges for the world economy of adopting a ‘world wide currency’, using a two-country world in which each country has its own national currency and national central bank, but where there is also a global currency in circulation. It suggests that Carney’s wish may be granted, but sooner than expected and in a different manner.