Wd be possible to devalue all currencies simultaneously under an international gold standard. But this would merely push up the gold price.— Frances Coppola (@Frances_Coppola) February 19, 2016
And that would raise the real value of the world’s monetary base, i.e. gold, which would tend to increase demand (the more money people have, the more they spend).
That’s called the “Pigou effect”. But of course that’s not a brilliant way of raising demand.