Okay - here's the first thing I've discovered.
Regarding Penguin 4.0 and people who have seen a decline in traffic since early 2017.
I believe Google may have released a Penguin related algorithm on the 1st of February 2017 that devalued backlinks that don't get clickthroughs. It was followed in the next few weeks by a spate of manual actions, and I think they were using it to surface link networks.
The update was referred to as the "Groundhog day update".
I read a Bill Slawski article here on it:
[
gofishdigital.com...]
Here's the relevant section:
"Demotion based upon a high number of links that don't produce much traffic"
"...a resource may be linked to by a large number of other resources, while receiving little traffic from the links. For example, an entity may attempt to game the ranking process by including a link to the resource on another web page. This large number of links can skew the ranking of the resources. To prevent such skew, the system can evaluate the "mismatch" between the number of linking resources and the traffic generated to the resource from the linking resources. If a resource is linked to by a number of resources that is disproportionate with respect to the traffic received by use of those links, that resource may be demoted in the ranking process."
This article makes it sound like the ratio between active (traffic) and inactive (no traffic) links is important and the result is an actual algorithmic demotion. For the page? For the site?
I first started my site in 1999 and I have a lot of links (100K) going back all that way from users who have shared my stuff on their websites and blogs. I doubt very much that links from the 2000s are going to give me much in the way of traffic.
Alexa says I have about 250-300 links with measurable traffic, about 50-100 less than another site that was started in 2012 that has a similar number of backlinks. The spammy new EMD that took over the niche in March has about 20 measurable traffic links in Alexa, but about 300 links in total, which is a much better ratio than either of us, plus those links are fresh.
I can't quite tell what they mean by demotion. It doesn't say the links are ignored, it says the resource (page) is demoted in rankings. Is the demotion proportionate to the value of the links, or disproportionate?
I believe this algorithm has considerably weakened the power of long-established sites like mine. I don't know whether it's an active penalty, but I believe it's made it very easy for new sites to easily outrank old sites, because old sites are getting their backlinks ignored.It means my carefully curated site has been outranked by people who are out to make a quick buck.
This algorithm may as well be called "Postmodern" because it's effectively removed the quality measurement - the best ranking measurement for my niche - which is user votes. It means one link (paid for or otherwise) from a news article or a big corporate site could outweigh hundreds if not thousands of links from ordinary people.
The article suggests that the effects of this algorithm can be mitigated by high quality scores - "the long click" engagement metric, but I'm not so sure. I don't know how they measure that metric or if it's working fairly, or whether they've added additional factors into that quality score system (like for example the on-page trust factors I've mentioned).
And of course in my own case I lost all of my Panda engagement metrics when I moved my pages off subdomains this summer when Google mucked up my https migration by ignoring my canonical tags, made https links to subdomains without SSL certificates, and forced me to move all of my pages on to my www domain at once (long story).
There's something really suspicious about the timing of this update, and either they didn't think it through or they don't care that legitimate sites with lots of old backlinks could get hit. This could make it much harder for an old site to rank its homepage, since home pages tend to have higher bounce rates, and people rarely spend long on the home page before navigating away.