Undoubtedly, like his many scholarly colleagues worldwide, Hirsch found a need in his career and research to effectively quantify the impact of his work and the work of others. Unlike many of his peers, however, Hirsch chose to personally tackle the problem and developed a formula to quantify the impact of research work. His solution considers the publication record of an individual, the number (Np) of papers published over n years, the journals (j) where the papers were published, and the number of citations (Njc ) for each paper. The result is a single number, the "h-index," which is a relatively simple and useful way to characterize the scientific output of a researcher. According to Hirsch, "A scientist 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." 

While this equation may produce a simple number, the factors that must be considered in the process of calculating it are incredibly complex. Never one to shy away from a challenge, this month Scopus has turbo-charged its database of over 15,000 peer-reviewed titles from more than 4,000 publishers including more than 23,850 academic journals by incorporating the h-index. Given its deep roots in the world of academic and scholarly publishing, Elsevier's Scopus has always recognized the importance of citations and references, including features that allow authors to view all the citations their articles have received and the ability to view those articles within the system. Last year, the company incorporated a variety of methods specifically to help evaluate citations, including Author Identifier, which features the ability to disambiguate sources with the same name, and Citation Tracker. 

According to Iris Kisjes, Scopus' marketing manager, "the Citation Tracker gives a very clear overview of how someone is performing over time. For example, if you are looking at tenure, you'd want to see if someone is consistent." She points out that this sort of tracking would also be applicable to substantiate funding, as government agencies could use Scopus to check whether a research group would be eligible for support.

To make Scopus more useful for its audience, however, Kisjes says they continue to look for the most current and accurate methods to help users evaluate research. She says, "The h-index has become accepted by the research market as a means of measurement, in that it is the most objective value out there at the moment. Including it in Scopus increases the reliability and quality of the citation tracking."

According to Kisjes, "There's a whole trend in the market, with the government setting performance measures for institutes. They have to start performing to get funding. Individuals also have to do this for career advancement, so tracking the value of research has become a hot topic in the market, and Scopus has provided a foundation to do this more effectively."

(www.elsevier.com; www.scopus.com)