From impact to importance

the current state of the wisdom-of-crowds justification of link-based ranking algorithms

George Masterton

Erik J. Olsson

pp. 593-609

in: Marcello D'agostino, Massimo Durante (eds), The governance of algorithms, Philosophy & Technology 31 (4), 2018.

Abstract

In a legendary technical report, the Google founders sketched a wisdom-of-crowds justification for PageRank arguing that the algorithm, by aggregating incoming links to webpages in a sophisticated way, tracks importance (quality, relevance, etc.) on the web. On this reading of the report, webpages that have a high impact as measured by PageRank are supposed to be important webpages in a sense of importance that is not reducible to mere impact or popularity. In this paper, we look at the state of the art regarding the more precise statement of the thesis that PageRank and other similar in-link-based ranking algorithms can be justified by reference to the wisdom of crowds. We argue that neither the influential preferential attachment models due to Barabási and Albert in (Science 286:509-512, 1999) nor the recent model introduced by Masterton et al. in (Scientometrics 106:945–966, 2016) allows for a satisfactory wisdom-of-crowds justification of PageRank. As a remedy, we suggest that future work should explore "dual models' of linking on the web, i.e., models that combine the two previous approaches. Dual models view links as being attracted to both popularity and importance.