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I am writing an academic essay (APA standard) in which I compare a lot of proportions (and probability estimations).

Phrases like

... are 5.2 percentage points more likely to ...

are common. So I want to use an abbreviation. But not sure if to use pps, PPs, pp, PPt, or just pp. Curiously, I find nothing from APA or anyone else when doing a quick web search looking for best practices. At this point any insights or standard I can follow is good enough.

Update

Percentage point is different from a percent (literally part of a hundred).

Example:

30 percent of customers complained about our service last year. This year only 24 percent.

So we would say there has been 6 percentage points decrease in complaint but the decrease is also 0.06/0.30 = 0.2 = 20 percent.

  • What's wrong with just "points"? – Azor Ahai Sep 15 '16 at 0:11
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    Not if you're discussing polls, or something else that uses percentage points. – Azor Ahai Sep 15 '16 at 0:22
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    @HotLicks That's a common misunderstanding. mathsisfun.com/percentage-points.html – snoram Sep 15 '16 at 1:19
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    Trust me on this one. Also here is another link: en.wikipedia.org/wiki/Percentage_point – snoram Sep 15 '16 at 1:46
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    The very fact that you are having to go to considerable pains to demonstrate to Hot Licks that "5.2 percentage points" differs fundamentally from "5.2 percent" is to me a strong indication that you shouldn't make the distinction even more difficult to grasp—which I think would happen if you shortened "5.2 percentage points" to anything else. My advice: Spell out "5.2 percentage points" in full, and promise yourself that you'll make up the difference by tightening up loose wording or removing superfluous content elsewhere in the text. – Sven Yargs Sep 15 '16 at 2:25
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I would suggest choosing any of these abbreviations, like pp, and clearly defining this for your readers at the beginning. I think using the abbreviation would actually make it less likely for someone to misinterpret what you are describing, since it is much more natural for people to assume we are discussing percent change (as evidenced by the initial interpretations of your question).

Wikipedia indicates that pp is used, but the reference provided seems to not directly support this. Other references indicate ppt may be used.

I would lean towards pp only because when I see ppt I think of "powerpoint" and this may be distracting for readers.

... are 5.2 pp more likely to ...


As a somewhat of an aside, this is definitely a less usual way of describing differences in proportions, so do be cautious about your phrasing. See this link for some examples of phrasing you might be able to use, which might even help clarify your point to your readers.

"...percentage of uninsured Americans rose by 9 percentage points."

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    +1 agree on ppt <-> Powerpoint . On the side note: "more likely to" makes sense if you are talking about change in probability. – snoram Sep 15 '16 at 0:48
  • I think you actually are correct in your phrasing. I think it just is a less common way of expressing the change. I will edit my answer to reflect this – gstats Sep 15 '16 at 1:15
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How about percent or %?

Each of the following is common parlance:

... are 5.2 percent more likely to ...

... are 5.2% more likely to ...

There is no abbreviation that I am aware of of the sort you've mentioned, and personally I see no need for one.

Addendum: I answered the question that was originally asked. Based on the update to the question, it is now obvious that the OP is seeking an abbreviation for percentage points as per the example in the update. So, for example, if 30% changed to 24% for some reason, that change would correspond to a decrease of 6 percentage points. The question is this: Is there a best-practice (broadly-accepted?) abbreviation for percentage points? Personally, I am not aware of one, but any author could adopt an abbreviation, such as pp or ppt or ppts or %pts, provided they define it so the reader can understand it. Maybe some other user will have a more satisfying answer.

Addendum: See my comment below on the difference between using decrease and difference. In my first addendum, I should have used "difference of 6%" rather than "decrease of 6 percentage points". Had I used difference, there would have been no need to talk about percentage points at all. In fact, one often sees the term percent difference or % difference, either of which can be positive, negative, or zero.

  • Not the same. See update to original post – snoram Sep 15 '16 at 0:16
  • @snoram Thanks for the comment. Your update was not there when I responded, and if it was, it appeared while I was composing my response. It changes the question. Actually, given your example, I would be tempted to go with the 20% decrease and not worry about percentage point differences. Everything is relative. – Richard Kayser Sep 15 '16 at 0:27
  • Yes. My update was sparked by your answer. Sorry for the confusion. But I suggest you delete or update your answer. – snoram Sep 15 '16 at 0:29
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    @snoram One more thought. The problem may relate to the difference between decrease, which you used, and difference. If 30% of something changed to 24% of something, you could characterize that as either a decrease of 20% (which I would tend to do, although decrease is somewhat ambiguous) or as a difference of 6%. If you were to use differences, you wouldn't have to worry about percentage points or abbreviations. Hope this helps. – Richard Kayser Sep 15 '16 at 13:48
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    This answer is problematic, as it is certainly not a valid answer to OP's redefined question. Since 'percentage points' was present from the start, the correct procedure before clarification would have been to close-vote on grounds of lack of clarity. 'There is no abbreviation that I am aware of of the sort you've mentioned, and personally I see no need for one....Maybe some other user will have a more satisfying answer.' certainly should not be receiving upvotes (and gstats provides abbreviations that have been used). – Edwin Ashworth Sep 15 '16 at 15:03

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