# Percent change vs. percent difference

What is the difference between percent change and percent difference? When would you use one over the other? Thanks.

phinds
Gold Member
What is the difference between percent change and percent difference? When would you use one over the other? Thanks.
Have you done any research on this? It's pretty easy to do it yourself.

symbolipoint
Homework Helper
Gold Member
You choose depending how specific you want to be in discussing or stating the change. If you want to avoid confusion, speak in terms of percentage increate or percentage decrease.

phinds
Gold Member
You choose depending how specific you want to be in discussing or stating the change. If you want to avoid confusion, speak in terms of percentage increate or percentage decrease.
That's not what the internet says. You are talking about % change, for which I agree w/ you, BUT ...
Percent Difference is the difference between two values divided by the average of the two values shown as a percentage.
which is not the same thing.

symbolipoint
Homework Helper
Gold Member
That's not what the internet says. You are talking about % change, for which I agree w/ you, BUT ...
which is not the same thing.
That shows you why I like to look for more precise language in discussing percent change or percent difference. Or at least show in symbolized form what is meant, to help cut through any troubles with language.

phinds
Gold Member
That shows you why I like to look for more precise language in discussing percent change or percent difference. Or at least show in symbolized form what is meant, to help cut through any troubles with language.
But all you said was
speak in terms of percentage increate or percentage decrease.
Which does not describe percent difference at all, that was my point.

phinds
Gold Member
What is the difference between percent change and percent difference? When would you use one over the other? Thanks.
@i_love_science, as @symbolipoint suggested, MATH (symbolic notation) is the best way to precisely describe things.

If something goes from 50 to 100, that's a percentage increase of 100%.

If something goes from 100 to 50, that's a 50% decrease

The percentage difference between 50 and 100 is 66.7%

SO ... you don't "use one over the other", you use the ONE that is correct for what you are describing.

DaveE
DaveE
Gold Member
In practice, you will often find some confusion in how people use percentages to evaluate change. This is where it's important to clearly communicate. Percentage is really just a fraction of some sort, The rest is, unfortunately, dependent on human language. It is fashionable in lectures to define these things, but out in the real world it's a mess; people do it in all sorts of ways. You really just need to ask them, read an equation, or, if you are the source, tell people what you mean.

atyy and symbolipoint
symbolipoint
Homework Helper
Gold Member
But all you said was

Which does not describe percent difference at all, that was my point.
and this part was left out of the quote, so needed to include
If something goes from 50 to 100, that's a percentage increase of 100%.

If something goes from 100 to 50, that's a 50% decrease

The percentage difference between 50 and 100 is 66.7%

Percent Change is not clear unless the number from which the change happened is known, given, or assumed, or if the assumption can clearly be understood.

Borek
Mentor
To avoid ambiguity when going from 5% to 10% you can always say "increased by 100%" or "increased by 5 percentage points", can't you?

phinds