[adventured]

> Mandarin would open the EU to the largest number of speakers

More people speak English than Mandarin and that language base represents a dramatically larger economy than Mandarin does.

The long-term trends favor English over Mandarin, not least of which is due to the difficulty of learning Mandarin vs English. The demographics underpinning Mandarin use are exceptionally bad in terms of direction, whereas the demographics underpinning English use globally are exceptionally good. The past 20 years has more than demonstrated the very low interest globally in Mandarin, despite the huge increase in China's importance and economy there has been no corresponding boom in the pick-up of Mandarin outside of China. In the next 20 years Mandarin will become a contracting language, while English will continue to expand globally. Over the time that China has been rapidly rising (since ~1990), English has only become more important globally, not less. Eventually, across this century, nearly as many people in China will speak English as Mandarin (they're very hard at work on achieving that; it'll be to their benefit and they full well know it).

[gumby]

> More people speak English than Mandarin and that language base represents a dramatically larger economy than Mandarin does.

Oh I agree but I was jocularly speculating on multiple constraints, to whit English is unacceptable as it would imply something favourable about those damned splittists; Spanish would not be acceptable because it would elevate one European country's language above others (though wasn't that the de facto story about English before Brexit?) etc etc.

In a different comment I argued for English because is not the selected language of any EU country.

Hmm, German might be a good choice as it is the EU language of three nations, so has a "majority vote" :-)