What is the h-index?
The h-index or Hirsch-index is a measure proposed in 2005 by a physicist named Jorge Hirsch at the University of California at San Diego as an objective index to compare the publication record and the citation record of an individual scientist.
A scientist has an index of h if his or her number of publications has at least h citations each and all his/her other papers have no more than h citations each. In other words, a scientist with an h-index of 20 has 20 papers each cited at least 20 times, and he/she can have many more papers that are cited less than 20 times each. Once established, this number can NEVER go down!
What is a GOOD h-index?
There is no simple answer. A scientist starting out will have low h-index while a mature scientist who publishes in multi-researcher groups in major research journals will have a high h-index.
Remember that the h-index is meant to measure the long-term career publication/citation of a scientist's works. According to Dr. Hirsch,
- For PHYSICS - 12 is typical for advancement to tenure at associate professor level and 18 is typical for advancement to full professor
- Overall, "an index of 20 after 20 years of scientific activity characterizes a successful scientist"
- "An h-index of 40 after 20 years of scientific activity characterizes an outstanding scientist at top universities or major research labs"
In biological sciences and medicine, each discipline and department will have a range of h-indices, depending upon many factors, including the length of years of publication, types of research, and emphasis of the faculty responsibilities.
How do I best understand the h-index?
Read the original paper:
- Hirsch JE. An index to quantify an individual's scientific research output. Proceedings of the National Academy of Sciences. 2005; 102:16569-16572.
- Do a Cited Reference Search to this paper in the Web of Science database and read the criticisms and defenses of this paper.
- Read our list of additional references about the h-index and impact factors (forthcoming)
Handout: How do I calculate the h-index? (PDF)