Interpreting SEO Data
Now that I have a minute to spare, I’d like to elaborate on my previous post, where I warned newbies not to accept all of Jonathan Leger’s conclusions. The particular post that made me question his ability to reason correctly was the one called Does PageRank Really Matter for Ranking in Google? (I have only read three or four posts on his blog so far, so one bad example out of four is a fairly poor average — maybe it is the only bad post though, I’ll have to read more to weigh in on that question.) His own data clearly shows PageRank does matter, yet he concludes it doesn’t. How can that be?
His data shows these results for the top ten links averaged for 500 keywords:
1. 6.722
2. 6.866
3. 6.292
4. 6.234
5. 5.968
6. 5.88
7. 5.73
8. 5.662
9. 5.656
10. 5.604
So how would that look if PageRank really didn’t matter? It would be a random distribution, so the overall averages would tend to be about the same for each position. I also suspect the numbers would be much lower, since the average PageRank for a random selection of pages would include far fewer high-ranked pages. I think an average around 2 or 3 would be much more probable, but regardless of what the actual number would be, it would be about the same for all positions, just varying slightly at random around the mean.
So how did Jonathan arrive at the brilliant conclusion that PageRank does not matter? He found that about one-third of the time a higher ranked page followed one of lower value. And 14% of the time it was a substantial difference (3 points of Pagerank or more).
So what does that tell us? It clearly demonstrates that PageRank is not the only factor that goes into the choice of what order result pages will be listed in — but that is a far cry from saying PageRank doesn’t matter at all! In fact it shows that most of the time (about 2/3 of the time) any two first-page results will be in PageRank order, with the higher ranked page on top. His own data refutes his conclusion.
Still, I like the fact that Jonathan actually tests things to see what effect they have. That is a step up from most Internet marketing advice, which is based on the consensus of guesses found on the forums.
2 Comments
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Hey there.
That 1-10 list would look precisely the way it looks now if PageRank doesn’t matter, because PageRank is a byproduct of having a lot of links to your site, and a lot of links mean good rankings. So naturally, since lots of links result in both a higher PageRank AND good rankings, it would APPEAR that PageRank has a big effect. The reality is, though, that it’s the links causing the ranking, and not the PageRank.
You see, I can go get a single link from a PR8 site, and in the next PageRank update my site would have a PR6 or PR7, but it wouldn’t rank for anything worthwhile because it only has one link to it! On the other hand, if I got thousands of links into my site, which resulted in a PR6 or 7, then I would easily be able to rank for substantial keywords. It’s not the PageRank that gets the site ranked, but the links. But since higher PageRank is a side-effect of having a lot of links to the site, it APPEARS PageRank matters much more than it does.
If PageRank was NOT the byproduct of links to the site, then you would be correct in saying that there would be an even distribution across the ranking points if PageRank didn’t matter. But since PageRank is the byproduct of links, and links are what cause the rankings, it will not be an even distribution at all — sites ranking higher will TEND to have a higher PageRank because more links generally means more PageRank. But the fact that this is NOT the case 1/3 of the time demonstrates that it’s not the PageRank causing the ranking. Further digging demonstrates that it’s the links to the page, and not the PageRank of the page, that matters.
I wish PR was a primary factor in ranking. If it was I would run out and get links from high PageRank sites and get a bunch of brand new sites with very few links ranked like crazy.
Thanks for the post.
Jonathan Leger
Comment :: January 10, 2008 @ 12:47 pm
Thanks for replying, Jonathan.
You measured PR and found a strong correlation. Certainly, correlation is not causation, so you could be right — but where is the evidence? I wonder why you would do such a study, only to dismiss the results as a byproduct of something you didn’t include in the study. On your own blog you say:
“When people make statements but fail to back them up with evidence, BEWARE!”
My point is not to say that PR is a primary factor in ranking — but that it is a good indication of how important Google thinks the page is. The same page will rank differently for each keyword/keyword phrase — there is no single overall ‘rank’ for a page. There is a single overall PR for a page, so it is a useful guide to how well you are doing in getting Google to consider your site important.
PR is also a useful factor to consider when working on getting incoming links. It is not the only factor — but given two sites of comparable authority, getting a PR0 link on one would not be as good as getting a PR5 link on the other. If getting those links requires effort on my part, I’m better off making the effort to get the PR5 link.
So PR does matter, even if it is a byproduct of good ranking rather than the cause (though your study does not show any evidence of that, you simply assert it without proof).
Comment :: January 11, 2008 @ 210:08 am