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The Vice and Virtue of PageRank (2019 edition)

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Den Prist
The Vice and Virtue of PageRank (2019 edition)

Let me tell you a story. In the beginning was PageRank, and it made Google the most powerful search engine.

Everything was great till PageRank stayed the secret sauce of Google's ranking mechanism and was talked about just in the research papers and technology pages.

However, once Google decided to make PageRank scores visible, it unleashed a flood of optimization strategies that were not exactly benign.

Let's look into what PageRank was, what PageRank is, and decide whether it was a blessing or a disaster for the Web.

Definition of PageRank

Page Rank Google

Page Rank (or PR in short) is a system for ranking webpages developed by Google founders Larry Page and Sergey Brin at Stanford University. It's used to give each page a relative score of importance and authority by evaluating the quality and quantity of its links.

Here's how it works. Each link from one page to another casts a so-called vote, the weight of which depends on the weight of the pages that link to it. And we can't know their weight till we calculate it, so the process goes in circles. There should be hell of a formula to calculate it.

However, it's much simpler than it seems.

Calculation of PageRank

Calculation of PageRank

Math is so cool that you can use a simple iterative algorithm and calculate the PageRank score of a page without knowing the value of other pages that link to it. How does it work? Each time we run the calculation, we are getting a closer estimate of the final value. We remember each calculated value and repeat the calculations a number of times till the numbers stop changing much.

In order to prevent some pages from having too much influence, the PageRank formula also uses a dampening factor. According to the theory, there's an imaginary surfer who is randomly clicking on links, gets bored at some point, and stops clicking. The probability that this person will continue clicking at any step is a dampening factor. In the formula, the total value of pages is damped down by multiplying it by 0.85 (a generally assumed value).

It's also considered that the average sum of all pages equals one. Thus, even if a page has no backlinks (i.e., no votes), it still gets a small score of 0.15 (one minus a dampening factor).

It's believed that Google recalculates PageRank scores after each crawl of the Web. As it expands, the initial approximation of PageRank decreases for all documents. Most probably, PageRank favors older pages as new pages cannot have a big profile of quality backlinks, so they receive lower scores.

The history of public PageRank (infographics)

The history of public PageRank

PageRank today

When something is invisible, it doesn't mean it doesn't exist. The same goes for PageRank. Google took out the scores from the public access, but PageRank stays its secret sauce ingredient. What's more, it still matters for rankings, as it helps the search engine determine the most relevant result for a particular query.

What's more, PageRank hasn't gone invisible in the minds of SEOs. You know how it goes: give something to an SEO, and he or she will reverse-engineer it. The exact same thing happened to PageRank. SEOs just didn't want to stay blind to the important things happening behind the scenes. This way, a bunch of SEO houses (e.g., Moz, Ahrefs, Majestic, etc.) took the original PageRank formula as inspiration and developed alternatives to the metric.

We in SEO PowerSuite also gave it a try and developed our own alternative — InLink Rank. Of course, we can never say that PageRank and InLink Rank are the same metrics. The only thing we can say for sure — InLink Rank is based on the original Google PageRank formula. The catch is in the fact that we don't really know how exactly Google implements the formula.

We ran an experiment to find out whether Google still uses PageRank and which of the existing alternatives matches Google results best. As PageRank scores are generally associated with search positions, we've explored the possibility of a correlation between the alternative metric and SERPs. Let's look at the methodology and results. More information you will find here.

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