Google PageRank Algorithm

PageRank is defined as a numeric value used by Google to show the value a page has on the internet. According to Google, all pages that have links to other pages are a benefit to that other page. If visitors go to a certain site from one particular page, then that page is ranked very important. When users visit a site from another page, that page votes for that page being visited. Google determines the value of a vote based on the importance of that web page to the search engine. To determine this importance, Google have come up with a system that enables them to calculate the importance of the page. The level of PageRank will determine if and where that page appears in search results.

Calculating PageRank
Google uses an equation to calculate PageRank. This equation is as below:

PR(A) = (1-d) + d(PR(t1)/C(t1) + … + PR(tn)/C(tn)

In that equation, the values t1 and tn are pages that are linked to the page whose rank is being calculated. The value C represents all outbound links on that page while‘d’ is the damping factor. This is normally calculated as a standard 0.85. Google also uses the term ‘share’ to calculate the final PageRank of a page. This is done by dividing the PageRank value by the outbound links that are on that page. This is the ‘vote’ that other pages have helped cast on the page to increase the rank. Therefore, Google shares out the number of ‘votes’ on that page for all pages that have ‘voted’ for that page so that they all get a point towards their PageRank. Therefore, the less outbound links there are on a page the higher that page will rank and that ‘vote’ will be valued more when linked to other pages.

According to many experts, Google uses an algorithm to calculate PageRank. This algorithm is not known by people other than Google. Like all algorithms, moving from level 1 to 2 will be much easier than moving from level 2 to 3. When calculating PageRank, previous positions do not count in that all other information is discarded and PageRank calculated afresh. If two pages without any other links ‘vote’ for each other, their PageRank values will be calculated based on each others PageRanks. Therefore, one of them will have inaccurate information as it was calculated based on the other’s PageRank, which had not been calculated yet. This will consequently lead to the second one having inaccurate information because it will also be calculated based on inaccurate data.

In order to get to a more accurate PageRank value, Google uses the newly calculated PageRank values to calculate slightly more accurate PageRank values. After repeating the calculations about fifty times, the difference between the results starts becoming negligible and Google gets its values at that point. However, based on this algorithm, it is almost impossible to have 100% accuracy rates for PageRank values. This is because the initial information used was not accurate and subsequent calculations were based on that information. This long process is the reason why PageRank updates take as long as they do.