# Talk:Percentage point

WikiProject Statistics (Rated Start-class, High-importance)

This article is within the scope of the WikiProject Statistics, a collaborative effort to improve the coverage of statistics on Wikipedia. If you would like to participate, please visit the project page or join the discussion.

Start  This article has been rated as Start-Class on the quality scale.
High  This article has been rated as High-importance on the importance scale.

## Ambiguity in 'twice as much'

someone please indicate the meaning of the 1st paragraph hypothesis... if population never changed, let's say 100 people. in the 80's 40% was smoking, in the 90's 30%. that's a reduction of 10 people. so, the change of 10 from 100, is 10%... where does the 25% cames from? — Preceding unsigned comment added by 99.56.198.134 (talk) 07:45, 3 December 2011 (UTC)

10 people who quit is 25% of 40 people who smoked. Abolen (talk) 20:01, 3 December 2011 (UTC)
Still "assuming the same total population in both years" is wrong. That only needs to be true if the 25% should also reflect on the change of the absolute number of people who. A reduction from 40% to 30% is a 25% decrease, no matter how the population changed. The whole reason of using % is to become independent of the absolute numbers. And 30%/40%=0.75=75% and that is always true. Therefore, I will remove the false statement. --92.224.55.215 (talk) 12:36, 21 December 2011 (UTC)

I disagree with this statement in the article: "Statements such as "between 1980 and 1990, the smoking rate decreased twice as much as the lung cancer rate" are ambiguous: it is not clear whether percentages or percentage points are being compared."

I don't see how it is ambiguous. By saying "the smoking rate decreased twice as much as the lung cancer rate" the speaker would merely be saying that the decrease of one was twice the value of the other. I see how a statement could be incorrect when a speaker misuses the term "percent" but that term is not mentioned in this sentence. When no specific unit is mention it is convention to assume the author is referring to absolute value. Therefore, one must also assume that if one were to nominate a unit of measurement to be applied to the value referred to as decreasing, then one would also have to apply the same unit of measurement to the the value with which it is being compared. After all, you don't very often hear a beef farmer say "my herd of cows has decreased by twice as many chickens as last year" do you now?

Shoutatthesky (talk) 09:20, 4 January 2012 (UTC)

Suppose smoking rate decreases from fraction 0.2 to 0.1 of the population, while lung cancer rate decreases from 0.01 to 0.005 of the population per year. Then the decreases here are either
• a fall in both cases by a factor 0.5
• a reduction of the fraction affected by 0.1 of the population in the first case, or 0.005 in the second case.
So here the "descrease" is either the same or different by a factor of 200 depending on whether change is measured multiplicatively or additively. It might be better to describle this avoiding percentages, but the article is about "percentage points". Melcombe (talk) 18:28, 6 January 2012 (UTC)
This is a case where a good reference would help and not having a reference means even though I don't disagree with anything in the article it very possibly is mostly WP:Original research. Dmcq (talk) 12:31, 30 January 2012 (UTC)
Some of this is discussed further in Relative change and difference, and perhaps all of the "measuring change" stuff could be moved/dealt with there. That article has a few external links/references, but I don't know if they are relevant to this particular point. Melcombe (talk) 13:43, 30 January 2012 (UTC)

## Symbol

What is the symbol of percentage point? — Preceding unsigned comment added by 188.67.25.97 (talk) 07:51, 8 July 2012 (UTC)

It's pp. But is there supposed to be a space before it? — Preceding unsigned comment added by 98.203.241.55 (talk) 22:45, 31 July 2012 (UTC)
Spacing before units is a typographical issue (and thus off-topic) and opinions vary. (FWIW, I would use a tiny, unbreakable space.) See Space (punctuation). — Preceding unsigned comment added by Hans Meine (talkcontribs) 15:47, 11 February 2013 (UTC)
Any source about the symbol being “pp”? Palpalpalpal (talk) 19:42, 20 March 2013 (UTC)

## Citation needed?

e.g. going from 1% to 9% is an 8 percentage point increase.[citation needed] Who point the citation needed tag in the opening line? Why? Why would a citation be needed for such an obvious fact? Is someone trying to suggest that they believe the increase is actually 8 percent?-- 23:21, 15 December 2014 (UTC)