Nature of the phenomenon
It illustrates the degree of interconnectedness or, as applied to society, the level of socialization of the phenomenon under study.
It originated in academic usage, where it serves as an important indicator of the overall scholarly merit of a given author's work.
As applied to the Internet, it denotes the technical degree of trust accorded to an information source.
How it works
In the simplest form of the citation index, only the number of links to a resource is counted.
The thematic citation index (tCI) also takes into account the subject matter of the sites linking to the resource, while the weighted citation index factors in the popularity of those linking sites (also calculated, in most cases, on the basis of the citation index).
Criticism
Before website optimizers appeared, the citation index genuinely reflected the popularity of the corresponding resource on the internet.
The first major search engine to make active use of the citation index was Google (the PageRank algorithm). In the Russian-language segment of the Internet, the best-known CI is that of Yandex (tCI, also nicknamed "Denezhka").