Citation tracking, or citation analysis, is a tool frequently used to trace scholarly research, measure impact, and inform tenure and funding decisions. The impact of an article is evaluated by counting the number of times other authors cite it in their work. Researchers do citation analysis for several reasons:

• find out how much impact a particular article has had, by showing which other authors have cited the article in their own paper.
• find out how much impact a particular author has had by looking at the frequency and number of their total citations.
• discover more about the development of a field or topic (by reading the papers that cite a seminal work in that area).

Caution! Citation analysis should be only one of many tools used to evaluate the quality, value, and impact of an author or institution's work. Click on the Cautions about Metrics tab on the left to find out why some measures are problematic, and how to think through evaluating your own and others' work.

The best known article level metric is the number of times an article has been cited. Cameron Neylon explains why new article-level metrics are needed. Technology and Open Access have made other types of metrics possible. Other article metrics include counting:

• page views
• downloads
• mentions in blogs
• inclusions in social bookmarking tools.

PLoS pioneered many of these new article metrics. They provide a great overview of the topic. BioMed Central indicates "most viewed" and "highly cited" cited articles and allows readers to comment on articles.

The Social Science Research Network (SSRN), a repository of social science articles, counts article downloads and provides lists of top articles, authors, and institutions based on the download counts.

See Altmetrics for more information about newer measures.