Abstract

We address the fundamental question why we should use PageRank and similar link-based algorithms in search engines, if at all. In a legendary article from 1998, the Google founders gave an intriguing wisdom-of-crowds justification for PageRank according to which the latter tracks quality online. This striking suggestion stands in contrast to the view that PageRank merely tracks what is popular. However, Masterton and Olsson showed that web-ecologies generated by Google-like assumptions essentially fail to reflect the scale-free structure of the web. They pointed to attraction to popularity or a rich-get-richer effect being the likely main cause of scalefreeness. In this article, we explore dual models of linking behavior, i.e. models that combine attraction to importance with attraction to popularity. Our results, obtained through computer simulation, indicate that there exist dual models that give rise both to a wisdom-of-crowds effect for PageRank and to scale-free web-graphs, thus giving a partial vindication of the wisdom-of-crowds thesis for the real web. Future work should explore larger web-graphs as well as other aspects pertaining to the empirical plausibility of dual linking models.