Bibliometrics uses quantitative methods to study scientific publications. These methods are based on the amount of publications and the number of citations that they have received.
Bibliometrics can be used to evaluate performance of individual researcher or to compare the research activities of a unit within a certain field. Analysis based on citations and publication amounts are potential tools in recruitments, career assessments, funding applications and in organizations internal evaluations. All of the best-known university rankings are also based on citation analysis. Also, the Finnish Ministry of Education and Culture considers Publication Forum as the primary tool for evaluating the quality of a journal, and the quality of publications affects the ministry funding allocated to the university.
Most commonly used bibliometric indicators are number of publications and citations, h-index and g-index.
The H-index, also known as the Hirsch-index is based on the amount of researcher's publications and the number of citations that they have received in other publications. Publications are organized in ascending order according to the most cited publication and then calculated where the sequence number of the publications meets the citations. A researcher has index h if h of his/her Np papers have at least h citations each, and the other (Np − h) papers have no more than h citations each. H-index can also be used to evaluate the productivity and impact of the research groups, institutes, universities, countries and scientific journals. H-index should not be used to compare different disciplines as publication practices vary. For example in Medicine and in Social sciences the amount of publications and citations differ greatly. H-index can be used to compare researchers from the same discipline if they have approximately equal career as a researcher. H-index can be found from databases like Web of Science, Scopus, Publish or Perish or SCImago Journal & Country Rank -site.
Hirsch, J. 2005, "An index to quantify an individual's scientific research output", Proceedings of the National Academy of Sciences of the United States of America, vol. 102, no. 46, pp. 16569-16572.
G-index is an indicator derived from the H-index. It takes into account the cumulative amount of citations received. If the amount of received citations are organized in decreasing order, the g-index is the (unique) largest number such that the top g articles received (together) at least g2 citations. G-index was established by Leo Egghe in 2006. According to Egghe, the main criticism towards H-index was, that the H-index does not take into account the actual number of citations of those highly cited publications (more than h). Amount of citations can be considerably higher than h.
Egghe, L. 2006, "Theory and practise of the g-index", Scientometrics, vol. 69, no. 1, pp. 131-152.
For example researcher, with one highly cited publication (137 citations) and several moderately cited publications (5-28 citations), H-index remains low (7) and G-index increases high (16), because the G-index is calculated by taking into account the total amount of citations.