Is the glass half empty, or half full?
I have heard that question posed many times, and never been happy with the standard answer. I’ve always believed there is no such thing as half empty. A 10 ounce glass with 5 oz in it is half full. (Half of zero is still zero — assuming your calculation does not consider it an error).
You can say, correctly I might add, that with 5 oz in it, when it formerly had 10 oz, it has been half-emptied.
But this is essentially a grammar, not philosophical problem.
The answer depends upon whether you are asking for the current volume, or the recent trend.