Research metrics are measures used to quantify the influence or impact of scholarly work. Some examples of this are bibliometrics (methods to analyze and track scholarly literature), citation analysis, and altmetrics (a more recent set of alternative methods that attempt to track and analyze scholarship through various digital media.)
The development of electronic indexes, Science Citation Index (1963) and Social Sciences Citation Index (1973), that traced citations to scholarly articles led to an offshoot database, Journal Citation Reports (1975), that displayed the journal impact factor. The journal impact factor is a widely used research metric though its use is often criticized. Science Citation Index, Social Sciences Citation Index, and the more recent Arts & Humanities Citation Index now form part of the Web of Science Core Collection database that can be used to find citations to individual works. The Scopus database was launched in 2004 as a direct competitor to Web of Science, providing citation tracking and journal metrics.
In 2005, Jorge Hirsch published a methodology called the h-index as a citation-based measure of a scholars total output. This has become a required measure in some fields.
There has been an explosion of new methodologies to measure and track impact through citations as well as interest in the idea of using alternative measures, or altmetrics, to gauge the influence or impact of scholarship based on attention in social media or article downloads.
Research metrics are used because of a desire for a quantifiable, objective means of comparing scholarship for purposes of promotion and tenure and to attract or grant funding. However, they all have weaknesses. Most of the criticism revolves around the limits of coverage of the databases used to create the metrics, failure to account for differences in scholarly output and citation rates among disciplines, and the over-reliance by administrators and funders on a single metric or on quantitative rather than qualitative metrics in judging scholarship.
This Guide contains information about what metrics are available and where they can be found. The information is organized by the level of measurement , i.e. individual articles or books, journals, authors, or institutions/research groups.
Snowball Metrics is an initiative of a number of research intensive universities worldwide to "agree on methodologies that are robustly and clearly defined, so that the metrics they describe enable the confident comparison of apples with apples. These metrics are data source- and system-agnostics, meaning that they are not tied to any particular provider of data or tools." The metrics are described in detail in the Snowball Metrics Recipe Book and some sources will label a particular metric with their symbol.