So this chart was looking at the percentage of positions that had one consistent URL. But I was also interested in if they don’t have one URL, how many is it? Is it two just swapping in and out all the time, or is it a larger number?

Now it turns out that looking across all of these SERP positions, all 40,000 SERPs in 14 days, all these positions, the majority of positions actually housed 4 URLs or more, which is a staggeringly large number.

So although there were some that were stable with just one URL, the ones that were fluctuating were fluctuating a lot over the course of this period.

Why so much change?

So why so much change? Well, there are a few answers, some more obvious, some less obvious.

I think the most obvious is we know Google has said in the past, I think about five years ago now, Google said they were doing, on average, seven daily algorithm updates.

So as well as the big ones that we hear about, there’s all of these small ones all the time. We can only assume that that number has gone up since then. So all of these daily changes, Google rolling out all of these tests that affect just a small percentage of SERPs, this is obviously going to cause a lot of fluctuation. Site changes as well.

If you think that SEO works, then you think that changing things on a website changes rankings, and people are changing their websites all the time. In any given SERP, the chances are ripe that one of the URLs or one of the sites that that URL is on is being played with today. Maybe the internal links have changed. Maybe it was linked to you from somewhere externally. Maybe the anchor text is updated.

Maybe it had some new content added, a new product. There will be all of these small changes. If the results are very close in their ranking ability, then you could imagine that they’re going to go up or down a little bit in this period.

Lastly, and I think maybe most controversially, we’ve been hearing a lot recently about the US vs. Google case and about some of the sort of exclusive data that maybe gives Google an unfair advantage.

A lot of what’s been coming out is about how they might be using user data to inform search results. Now there have been experiments in the past, by people like Rand Fishkin, showing how you can affect real-time ranking changes using user data, as in if you ask everyone in a big room to go and click on position 2 or 3 on a SERP, then that result will move its way upwards, this kind of thing.

So maybe some of this reactive data is filtering through and affecting SERPs in real-time. We don’t know, but it’s possible.

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