PageRank Sculpting and Prevention Algorithms
PageRank algorithms are used to order search engine results based on relevance and importance, relating to the number of incoming and outgoing links to a site. However, website marketers often use methods of PageRank manipulation to maximize PageRank scores for particular websites. One such method is known as PageRank sculpting: the method of controlling PageRank flow using “dofollow” and “nofollow” links. In order to direct a higher PageRank flow towards “dofollow” links, markets assign a “nofollow” attribute to certain useless links in order to make the links they do care about matter more in terms of PageRank. For example, suppose a webpage has 10 total links. But 3 out of these 10 links have a “nofollow” attribute. The PageRank score will then only distribute to the remaining 7 links with the “dofollow” tag. Instead of splitting a value among 10 links, the same value is getting split along 7, thereby giving the 7 links a higher PageRank and more importance.
However, Google engineers have since developed methods to detect sculpting and negate the ramifications of this type of manipulation. Instead of giving priority to the “dofollow” links, Google now has algorithms that detect the presence of “nofollow” attributes. After detection, the “nofollow” attribute is then canceled so that PageRank still flows through that link. Additionally, the PageRank value for that “nofollow” link is canceled as well. So the use of sculpting is not beneficial anymore as it harms the website. Following the example above but this time using a prevention algorithm, the PageRank would flow to all 10 links regardless of their attributes. The 3 links with the “nofollow” tag would then be canceled, along with their PageRank flow. This would result in a lower PageRank value for the 7 “dofollow” links than in the scenario where the “nofollow” links were not present. I believe that this is a clever way to prevent PageRank manipulation because not only is the user not incentivized to use PageRank manipulation anymore, but also has the fear of losing out on PageRank flow if sculpting is detected.
This is an extension of the computation of PageRank as discussed in lecture, since the homework problem set about PageRank did not account for the presence of “nofollow” links that could possibly be used. With PageRank sculpting, the updates will include the “nofollow” thus resulting in a higher PageRank for the “dofollow” pages. This is assuming that methods to prevent sculpting are not in place. If methods described above were in place and did prevent sculpting, there would be lower PageRank equilibrium values.
How PageRank Sculpting Works:
https://seo-hacker.com/pagerank-sculpting/