google pagerank history

“PageRank does not rank web sites as a whole, but is determined for each page individually. Further, the PageRank of page A is recursively defined by the PageRanks of those pages which link to page A.”

“Google combines PageRank with sophisticated text-matching techniques to find pages that are both important and relevant to user’s search. Google examines all aspects of the page’s content (and the content of the pages linking to it) to determine if it’s a good match for user’s queries.”

“Google calculates pages PRs once every few months (PR update). After a PR update is done, all pages are assigned a new PR by Google and you will have this PR until a new PR update is done. New sites that were just launched will have a PR of 0 until an update is done by Google so that they are assigned an appropriate PR.”

“Google PageRank is calculated all the time, but what we see in the Google Toolbar (or other online PR tools) is a snapshot in time which is updated every 3 months or so.”

PageRank values don’t range from 0 to 10. PageRank is a floating-point number. “It’s more accurate to think of it as a floating-point number. Certainly our internal PageRank computations have many more degrees of resolution than the 0-10 values shown in the toolbar.”

“We’re sure that their curve is similar to an exponential curve with each new “plateau” being harder to reach than the last. I have personally done some research into this, and so far the results point to an exponential base of 4. So a PR of 6 is 4 times as difficult to attain as a PR of 5. [..] The difference between a high PR of 6, and a low PR of 6, could be hundreds or thousands of links.”

“PageRank is believed to be calculated on a logarithmic scale. What this roughly means is that the difference between PR4 and PR5 is likely 5-10 times than the difference between PR3 and PR4. So, there are likely over a 100 times as many web pages with a PageRank of 2 than there are with a PageRank of 4. This means that if you get to a PageRank of 6 or so, you’re likely well into the top 0.1% of all websites out there. If most of your peer group is straggling around with a PR2 or PR3, you’re way ahead of the game.”

“The fact is that PageRank is based on incoming links, but not just on the number of them. Instead PageRank is based on the value of your incoming links. To find the value of an incoming link look at the PR of the source page, and divide it by the number of links on that page. It’s very possible to get a PR of 6 or 7 from only a handful of incoming links if your links are “weighty” enough.”

“Google tries to find pages that are both reputable and relevant. If two pages appear to have roughly the same amount of information matching a given query, we’ll usually try to pick the page that more trusted websites have chosen to link to. Still, we’ll often elevate a page with fewer links or lower PageRank if other signals suggest that the page is more relevant. For example, a web page dedicated entirely to the civil war is often more useful than an article that mentions the civil war in passing, even if the article is part of a reputable site such as Time.com.”

Links don’t give PR away, they are votes. “When a page votes its PageRank value to other pages, its own PageRank is not reduced by the value that it is voting. The page doing the voting doesn’t give away its PageRank and end up with nothing. It isn’t a transfer of PageRank. It is simply a vote according to the page’s PageRank value.”

“We know from the paper “The Anatomy of a Large-Scale Hypertextual Web Search Engine” (Paper) that the PageRank of a Web page is a number calculated using a recursive algorithm in which the page receives a share of the PageRank of each page that links to it.”

Crawlers don’t analyze web-sites permanently. “It often takes two full monthly updates for all of your incoming links to be discovered, counted, calculated and displayed as backlinks.”