What is the h-index and why it is so important for science?

The h-index is a unique and useful tool for scientists to analyze the impact of their academic work. It is an author-level metric that attempts to measure both the productivity and the citation impact of the publications of a scientist, a scholar, a researcher, or an organization.

   The above index is based on the set of the scientist's most cited papers and the number of citations that they have received in other publications. Furthermore, the h-index can also be applied for analyzing a scholarly journal as well as a group of scientists, such as a department, a university, or even a whole country.

   The letter h stems from its founder. The index was suggested in 2005 by Jorge E. Hirsch, a physicist at University of California San Diego (UCSD), and it also called the Hirsch index or Hirsch number.

   H-index is defined as the situation in which a scholar with an index of h has published h papers each of which has been cited in other papers at least h times.

   It reflects both the number of publications and the number of citations per publication. The index is designed to improve upon simpler measures such as the total number of citations or publications.

   However, the h-index works properly only for comparing scientists working in the same field, and in general it is affected by field-dependent factors. You can find an automated h-index across different programs, such as Harzing's Publish or Perish program, which calculates the h-index based on Google Scholar entries. Other databases such as Scopus and the Web of Knowledge provide automated calculators too. Meanwhile, Google have provided an automatically-calculated h-index within their own Google Scholar profile.

   To sum up, Hirsch suggested that (for physicists) for faculty at major research universities, h of about 12 might be a typical value for advancement to tenure (associate professor) and that h of about 18 might be a typical value for advancement to full professor. In addition, 15 to 20 could mean a fellowship in the American Physical Society, and 45 or higher could mean membership in the United States National Academy of Sciences.

Reference:

Hirsch JE. An index to quantify an individual’s scientific research output. Proceedings of the National Academy of Sciences of the United States of America. 2005;102(46):16569-16572. doi:10.1073/pnas.0507655102.