# h-Index

The h- index ( Hirsch index, Hirsch factor also, stag Coefficient or h -number ) is a bibliometric measure based on citations of publications of an author at a time. A high h- index speaks for major scientific impact of the author. The index h of the author can not decrease over time.

## Definition

A scientist has a Hirsch index h if h of his total N publications have at least h times, the remaining (N - h) publications have been cited more than h times. To determine you can line up all the publications descending according to the author citation frequencies. You count by now, until the r-th publication has less than r citations. h is then r - 1

## Examples

Some examples of authors, each with 10 items:

- In citation frequencies 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 is the deer a factor of 5 because five publications at least five times, and the remaining were cited more than five times. The sixth release was also cited five times, but it can not be counted, because the deer factor would increase to 6, and five citations thus would no longer suffice.
- In citation frequencies 200, 200, 2, 2, 2, 2, 2, 2, 2, 2 is the deer a factor of 2 because two publications at least twice, and the remaining were cited more than twice.
- In citation frequencies 65, 58, 55, 17, 2, 2, 1, 1, 0, 0 is the deer a factor of 4, because four releases at least four times, the rest have been cited more than four times.

An example with the time factor:

- When publishing the first working this is not quoted. The author has the stag factor 0
- The work will eventually cited for the first time. The author has the stag factor 1
- The author is again quoted as saying. He keeps the deer factor 1
- The author writes a new article. He keeps the deer factor 1
- The second article is cited once. He keeps the deer factor 1
- The second article is cited a second time. Now he has the deer a factor of 2
- The next five articles appear to be without quotes. He keeps the deer a factor of 2
- After some time, all the items are quoted exactly twice. He keeps the deer a factor of 2
- Two studies were particularly interesting and are each 10 times cited. The other only twice. The author reserves the deer a factor of 2
- A new groundbreaking work appears and is cited immediately after publication twice. The author reserves the deer a factor of 2
- As this third work a third time is quoted, the Hirsch factor increased to 3
- The author now has three works that are cited 10 times each, and five more that are cited only twice. Hirsch factor 3
- Someone quoted all the works of the author in an article. The deer factor remains at 3
- The author writes another 10 articles, however, are nowhere cited. The deer factor remains at 3
- A far only three times cited article is cited a fourth time. The deer factor rises to 4

## Background

The h- index to evaluate scientific achievements was developed in 2005 by physicist Jorge E. Hirsch Argentine and published in the Proceedings of the National Academy of Sciences.

The data basis for the calculation of this factor a variety of data sources are conceivable. However, Hirsch himself has suggested, largely to use the data from the Web of Science, as these are currently the most reliable and comprehensive data base.

### Pros and Cons

The h- index has some advantages over other indicators ( such as the total number of citations of an author or the impact factor ), since the citations of a single, much - cited publication not have much impact on the index. This can also be interpreted as a disadvantage, since any breakthrough products can not be honored accordingly ( it comes almost to a harmonic approximation of the evaluation of quotes). In addition, neither the number of co-authors nor the fact is taken into account, whether the cited publication is an original work or a review article. In general, it should be noted that the ( different founded) "popularity" and not necessarily the scientific relevance is measured by a publication citations.

Furthermore, the data basis proposed by Hirsch ( Web of Science of the Institute for Scientific Information, ISI) but is not recognized, for example, book publications, which may alter the results of the rankings again. The collection of this data base is to be the greatest difficulty dar. In particular, the distinction between authors with the same name is a very big problem. Another problem in the social sciences and humanities is also that publications such as book reviews may be significant, but this hardly quoted and are thus not taken into account by the h-index.

The extreme importance that have the h- index and comparable bibliometric measures of the career of researchers, leading to optimization strategies that have a negative impact on the scientific culture. So it may be about purposeful to incorporate gaps or minor errors in a publication so that other authors criticize these errors and this quote the erroneous publication. Another possible strategy is to form groups ( " schools of thought " ) of 10 to 15 scientists who create their own magazine or similar publication medium therein cite each other frequently.

### Bestabschneidende scientists

Very well-known physicist reach loud stag a stag - factor of 62 to 107 At the time of publication of Hirsch index Edward Witten had 120 the highest h- index among physicists. In the life sciences famous scientists even reach an h- index of 120-191, which is also related to generally increased publications in this field.