What are Bibliometrics?

Measures of a scientific writer's influence are called bibliometrics. Techniques for discerning this influence, or impact, range from simple counts of publications to sophisticated mathematical equations. Two of the most well-known bibliometrics are the impact factor, typically applied to journals, and the h-index, typically applied to authors. 

What is an Impact Factor?

The impact factor, proposed by Eugene Garfield, is a ratio between citations and recent citable items published. Thus, the impact factor of a journal is calculated by dividing the number of current year citations to the source items published in that journal during the previous two years by the number of published articles in that journal during the previous two years.  Journal Citation Reports calculates and publishes the annual impact factors for journals. A higher impact factor generally indicates that this journal's articles have been cited more.

What is an h-index?

The h-index was proposed by Jorge Hirsch in 2005 as an alternative to the impact factor. The h-index quantifies scientific productivity and the impact of a scientist based on the set of his/her most quoted papers and the number of citations that they have received in other people's publications. For example, an author or journal with an h-index of 30 has written at least 30 papers that have each had at least 30 citations. Thus, a higher h-index indicates more publications that have been cited more often. This metric is useful because it takes into account the uneven weight of highly cited papers or papers that have not yet been cited.

How many times have you been cited? What's your h-index?

Scopus : Search for your name in the Author Search. In the list of authors that comes up in the search results, click on Details. The Details page provides both the times cited and the h-index, with links to graphs and tables.

Web of Science : Register for  ResearcherID to get your bibliometric data.

Google Scholar : Use the Author name field in the  Advanced Search form to search for yourself. Google Scholar only provides citation counts for individual articles, not an author's entire career. 

Below is a short list of selected articles. For a more extensive list of bibliometrics articles, try searching  Scopus or  Web of Science with search terms such as  bibliometrics OR "h-index" OR "impact factor". You can also run a more limited search in PubMed by clicking here. 

Ball, Philip. 2005. Index aims for fair ranking of scientists. Nature 436 (7053):900.
http://dx.doi.org/10.1038/436900a 

Bornmann, Lutz, and Hans-Dieter Daniel. 2005. Does the h-index for ranking of scientists really work? Scientometrics 65 (3):391-392. http://dx.doi.org/10.1007/s11192-005-0281-4 

2007. What do we know about the h index? Journal of the American Society for Information Science and Technology 58 (9):1381-1385.
http://dx.doi.org/10.1002/asi.20609 

Bornmann, Lutz, Rdiger Mutz, and Hans-Dieter Daniel. 2008. Are there better indices for evaluation purposes than the h index? A comparison of nine different variants of the h index using data from biomedicine. Journal of the American Society for Information Science and Technology (5):830-837.
http://www3.interscience.wiley.com/cgi-bin/fulltext/117908948/HTMLSTART

Costas, Rodrigo, and Mara Bordons. 2007. The h-index: Advantages, limitations and its relation with other bibliometric indicators at the micro level. Journal of Informetrics 1 (3):193-203.
http://www.sciencedirect.com/science/article/B83WV-4NCK2JT-1/1/ddf6c25f8810c462fb8c22ae3d5b5d28

Craig, Iain D., Andrew M. Plume, Marie E. McVeigh, James Pringle, and Mayur Amin. 2007. Do open access articles have greater citation impact?: A critical review of the literature. Journal of Informetrics 1 (3):239-248.
http://www.sciencedirect.com/science/article/B83WV-4P18BNV-1/1/0d60463e068ba604e67030229ce6d33b

Eysenbach, G. 2006. Citation advantage of open access articles. PLoS Biol 4 (5):e157.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=16683865

Garfield, E. 1999. Journal impact factor: a brief review. CMAJ 161 (8):979-80.
http://www.cmaj.ca/cgi/content/full/161/8/979

2006. The history and meaning of the journal impact factor. JAMA 295 (1):90-3. http://jama.ama-assn.org/cgi/content/full/295/1/90

Hirsch, J. E. 2005. An index to quantify an individual's scientific research output. Proceedings of the National Academy of Sciences of the United States of America 102 (46):16569-16572. http://www.pnas.org/content/102/46/16569.abstract

Leydesdorff, Loet. 2008. Caveats for the use of citation indicators in research and journal evaluations. Journal of the American Society for Information Science and Technology 89 (2):278-287.
http://www3.interscience.wiley.com/cgi-bin/fulltext/116839393/HTMLSTART

Lipsky, P. E. 2007. The lack of impact of the 'impact factor' in clinical medicine. Nature Clinical Practice Rheumatology 3 (4):189.
http://dx.doi.org/10.1038/ncprheum0462

MacCallum, C. J., and H. Parthasarathy. 2006. Open access increases citation rate. PLoS Biology 4 (5):e176.
http://dx.doi.org/10.1371/journal.pbio.0040176 

Molinari, Jean-Francois, and Alain Molinari. 2008. A new methodology for ranking scientific institutions. Scientometrics 75 (1):163-174.
http://dx.doi.org/10.1007/s11192-007-1853-2

PLoS Medicine Editors. 2006. The impact factor game. It is time to find a better way to assess the scientific literature. PLoS Medicine 3 (6):e291.
http://dx.doi.org/10.1371/journal.pmed.0030291

Schreiber, Michael. 2008. An empirical investigation of the g-index for 26 physicists in comparison with the h-index, the A-index, and the R-index. Journal of the American Society for Information Science and Technology 59 (9):1513-1522.
http://dx.doi.org/10.1002/asi.20856

Thomson Reuters. 2008. Using bibliometrics: a guide to evaluating research performance with citation data [white paper].
http://scientific.thomsonreuters.com/news/newsletter/2008-07/8465001/

Wikipedia contributors. 2008. H-index. Wikipedia, the Free Encyclopedia,
http://en.wikipedia.org/wiki/H-index