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Maybe this is a dumb question, but is it valid to have a negative percent below -100% when comparing two quantities?

I'm evaluating the Net Present Value of an investing project affected by many external variables. The expected NPV of the project is 122961$. When affected by external varialbes, the worst case scenario makes the NPV equal to -11128, which means a deviation of -109%. Does this have a valid meaning?

user35032
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  • When talking about percentages, it must be made perfectly clear "percentages of what." When we talk about milk for example... we might have "2% milk" vs "Skim milk." Is the 2% in "2% milk" that only 2% of the total liquid in it is milk., that it has only 2% the usual amount of fat? That it has 2% the recommended daily intake of fat per serving? That 2% of the total volume is fat? If you just say a percent by itself it is almost meaningless. If you clarify what the percentage is of however, then it should be clear that they can be any value depending on context. – JMoravitz May 01 '19 at 00:39

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Yes, it makes sense.

You are saying that the worst-case NPV is $109\%$ less than the expected NPV.

However, it just sounds a little awkward, but the point comes through.

It sounds normal to say "stocks increased $200\%$" to represent stocks tripling in value, but since $-100\%$ means $0$, it's not common to use such percentages.

Saketh Malyala
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