The "h-index" was introduced in 2005 as a metric for estimating "the importance, significance and broad impact of a scientist's cumulative contributions." It takes into account both the number of an individual's publications and their impact on peers, as indicated by citation counts. Its creator, Jorge Hirsch (UC-San Diego) asserts that a "successful scientist" will have an h-index of 20 after 20 years; an "outstanding scientist" will have an index of 40 after 20 years; and a "truly unique individual" will have an index of 60 after 20 years or 90 after 30 years. You can read more about it in Nature and PhysicsWeb.

Curious to know your own h-index? You can easily determine it using Web of Science. Select "Science Citation Index Expanded." Click "General Search" category and search for your name as author (e.g., SMITH J*). Use "Refine Your Results" by Institution to differentiate yourself from other scientists with the same initial(s). (This is an important step, otherwise your publications will be intermingled with unrelated papers and your h-index will be inaccurate.) Click on "Citation Report" in the box on the right side. Your h-index will be calculated automatically.

An alternative method is to sort your citations by "Times Cited", using sort box on the right side. Scan down the list until the number of the paper exceeds the number of citations to that paper. For example, your h-index is 20 if your 21st paper has been cited 20 or fewer times, but your 20th paper has been cited 20 or more times.