I believe the "ideal" - at least when you assume central banking - is a perfect fit between the expansion of the money supply and the "value" it represents - IO

I believe the "ideal" - at least when you assume central banking - is a perfect fit between the expansion of the money supply and the "value" it represents - IOW, a dollar/pound/ruble means the exact same thing, year by year. That would amount to population grown ( which is lagged by the age at which people go to work ) and productivity growth. I believe that describes "zero inflation" but it's sort of hard to say. It is possible that the previous evils of deflation no longer apply ( because technology) , but I'd rather not find out through experiment.