Q. What is an H-Index?

H index is an interesting metric, with myriad pros and cons. 

The short version is that H-index is intended to reflect both the productivity and the impact of any given author. Part of its elegance is that eliminates publications that skew an author’s output. If someone publishes an article in 1998 that is cited 4,000 times but then only publishes low-impact articles for the next 20 years, H-index takes that into consideration. However, a citation is considered a citation, whether or not it is positive. Additionally, it does not take into account where you sit in the authorship, or the quality of the publication in which it is published.

So here is how it works:

H-index is the number of articles published by an author (H) for which an author has been cited by other authors at least that same number of times (H). Read on, this will make sense in a moment!

SO, an H-index of 10 means that an author has at least 10 papers that have each been cited at least 10 times. If an author published another paper but it is only cited 7 times, the H-index remains 10.  Another way of understanding it is to take a look at a list of citations

This author would have an H-index of 6, because of the 7 papers published, only 6 have been cited at least 6 times. If over time, paper 5 gains more citations, that H-Index would bump up to 7. And if more papers are published, there is the potential for a higher H-index.

Two things to note:

1. Different databases score h-index differently because they define a citation differently or index different articles within different date ranges. This is most notable for Google Scholar, which holds a looser definition for article citation.
2. A “good” h-index is impossible to define because it is entirely dependent on the length of the career, how many articles are published, the field you are in, etc. A general rule that gets thrown about is that an h-index that matches the number of years you have been active is great. But that doesn’t take into account the variations that can happen across different fields and teaching loads.

To learn more about impact metrics and publications, please visit the Netter Library Writing & Publishing Guide.