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It’s actually one of the most publicly documented aspects of the company, but never under the word ‘coefficient’ because the copy-writers (the linguists deciding how Facebook talks about itself on the site and in its blog posts, a surprisingly influential group) really hate the word. They manage to rephrase every interaction into a phrase, typically “how close you are with them”.

One recent example of a TechCrunch guide on News Feed [1] where “Creator” is actually coefficient or a more recent official version [2]. There was a very early “How does Facebook work?” company blog post that explained a surprisingly large amount of things. It was the only official resource for a long time. The explanations were clear, if read the euphemism “how well you know them” as (a rather obvious for data-engineers) “we batch-compute a rating on a dyadic graph at regular intervals (yes, that means weekly)”. Without that idea that all those phrases correspond to the same constant, that blog post and its successor are rather unhelpful.

Coefficient-ranking is indeed omnipresent internally, to the point employees regularly use the word in front of civilians without realising you are not meant to, almost daily. Explaining the concept and or even saying it’s called “coefficient” is fine: those blog posts are considered clearly explaining those by the PR team. You are simply advised to phrase things in a more humane way, like the blog posts do, because that helps people understand (it doesn’t: admitting a single constant number is imperfect helps a lot people understand the issues they have with the News Feed).

It’s mainly used both in front-end for suggesting interactions and as a data-engineering filter: the list of every friendship is a trillion long.

[1] https://techcrunch.com/2016/09/06/ultimate-guide-to-the-news...

[2] https://newsroom.fb.com/news/2018/05/inside-feed-news-feed-r...

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