Those interested in this may like to know that The Economist publishes a style guide in book form:
https://www.amazon.com/Style-Guide-Economist-Books/dp/161039...
https://www.amazon.com/Style-Guide-Economist-Books/dp/161039...
https://cdn.static-economist.com/sites/default/files/pdfs/st...
I can’t help thinking that they would sell more copies of the full book if they made it clearer in that PDF that it’s just an excerpt!