1

I'm doing some work in a domain where it is normal to say that if the value was -1 and is now 2 There has been a +300% change.

To give some other examples:

  ( 10,  5) ->  -  50%
  ( 10, -5) ->  - 150%
  (-10,  5) ->  + 150%
  (-10, -5) ->  +  50%

Ie. if the value was 10 and it's now 5, there has been a 50% decrease. If the value was 10 and it's now -5, the change has been a 150% decrease. Etc.

The equation is: $$\frac{\text{value_latest} - \text{value_previous}}{abs(\text{previous_value})}$$

Does this calculation have a name? I am trying to research some of it's properties but I'm not sure what to google.

MYK
  • 131
  • It is a strange idea to consider the percentage change if negative numbers are allowed. Maybe someone can mention a situation where this idea has actually a merit since I cannot imagine such a situation. – Peter Jan 31 '22 at 13:58
  • It's common in finance. Eg "Profits are up 600% from a $10 loss last year to a $50 gain this year". I fully grasp that this is not what percentages are meant to be - but think of it as a domain specific definition. – MYK Jan 31 '22 at 14:02
  • @ryang - your link to "Relative Change" is exactly what I was looking for - if you post it as an answer I'll accept it. – MYK Jan 31 '22 at 14:05

1 Answers1

0

Perhaps ‘change relative to the absolute value’, or ‘relative error’ (as opposed to ‘relative change’) ?

Wikipedia: http://en.wikipedia.org/wiki/Relative_change_and_difference (sections 2 & 4).

ryang
  • 38,879
  • 14
  • 81
  • 179