Keyword density was super important for a decade or more

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  George G.: keywords are still important, but in the context of semantic search engines, you should focus on the entities.
  
  and keyword density is still important since if you overdo it, you can trigger an overoptimization filter. (especially in the headings)
  
  
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  Perry Bernard: The reason why tools still pimp the concept is because their software development is far behind the semantic matching capabilities of Google’s AI systems. They can only pimp what they are able to measure, and you’re right to point this out as a possible issue.
  
  
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  Travis Bailey: There is something to be said for focusing on a keyword. But a page at 99.9999999% density for a focus likely won`t beat a 1% focused page. I`ve also never seen a Goldilocks percentage predictably hit any specific targets regularly.
  
  If you`re doing a subject any justice, you`ll likely mention the subject at least a few times. And you definitely wouldn`t want to just paste `subject subject subject subject` somewhere near the footer - just to get some kind of `density` score.
  
  Keyword spamming did work way back in 2001, on Google. At some point in the earlier part of the last 20 years there may have been a point where being mildly spammy was viable. Definitely not so much anymore.
  
  
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  Michael Martinez: None of the search engines in existence today ever used keyword density. They do map word repetition, and many people mistake that for a keyword density analysis. To some people it`s six of one, half dozen of the other, but 50 occurrences of a word in a 1, 000-word article have a different density from 50 occurrences in a 1200-word article - and either way the repetition would be just as good or bad.
  
  
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  Chris Edwards: Google bought Applied Semantics in 2004, it appears that it`s taken many `experts` 17 years to work out what semantics are all about (OKay they all got siderailed by the damned misuse of LSI keywords)
  
  
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  Jaroslaw Pidburskyj: I still use it and it’s a major factor
  
  
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  Stockbridge Truslow: IMO, Keyword density was never really a factor. It tended to correlate with results but it was never the cause. Keyword "spread" was more likely a factor at one point though - but I`m not sure it was ever much of one.
  
  The tools picked it up because... math.
  
  Someone found a correlation of data that looked good. Whether one side of the equation is the actual cause of it, you can present it and sell it easily. Bonus points on this one because a 5th grade student could write the computer formula used to determine keyword density in a page.
  
  Keywords / Total Words = Density.
  
  So now you have a demand for a spurious correlation and you`ve got a program that took you 12 minutes to write that meets that demand. I`d put that in my tools if I made them, too.
  
  
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  Stockbridge Truslow: Ohhhh. I did just think of a situation where keyword density mattered, but not in the positive sense.
  
  If your keyword density is too much, you used to be able to trip the spam filters by virtue of that (and just about that alone). But if you match your competitors, you`re probably safe.