How important is traffic as a ranking signal?

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

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  Steve Gerencser: Let me ask you a different question. How can Google know how much traffic each website gets? If Google can not possibly know all of the traffic that every website gets, how can it be a ranking factor?
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  Alan Bleiweiss: With the Advent of universal search, and position zero, it is possible to be ranked #1 organically and have a low click rate due to people clicking on map results, answer box, knowledge graph, or carousel results, and where you can remain #1 organically for a long time. Also, experimenting with page titles and meta descriptions can sometimes result in more clicks, as one option to work to improve CTR.
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  Micah Fisher-Kirshner: I`ve seen it (ranking for highly competitive keywords with little traffic to the page), though to be fair, it`s competitive in the sense that it`s competing for another company`s brand terms...
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  Jacob Punton: If I`m understanding this correctly, then here`s something I found on Backlinko: 131. Direct Traffic: It’s confirmed that Google uses data from Google Chrome to determine whether or not people visit a site (and how often). Sites with lots of direct traffic are likely higher quality than sites that get very little direct traffic. (SOURCE: http://backlinko.com/google-ranking-factors)
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  Roger Montti: Traffic is not a ranking signal. In fact, "ranking signals" are only what happens in the ranking algorithm. There are other algorithms outside of the core ranking algorithm that can set those aside and rank other sites entirely.
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  Neil Cheesman: Perhaps it isn`t the `traffic` itself - but how the `traffic` behaves.... ie time on site/bounce back to SERPS