surfing the research literature on your lunch break and find an
unfamiliar author listed on a great new publication. How do you size
them up in a snap?
Or do you?
is an attempt to sum up a scholar in a single number that balances
productivity and impact. Anna, our example, has an h-index of 25 because
she has 25 papers that have each received at least 25 citations.
Today, this number is used for both informal evaluation (like sizing
up colleagues) and formal evaluation (like tenure and promotion).
We think that’s a problem.
1. Comparing h-indices is comparing apples and oranges.Let’s revisit Anna LLobet, our example. Her h-index is 25. Is that good?
Well, “good” depends on several variables. First, what is her field
of study? What’s considered “good” in Clinical Medicine (84) is different than what is considered “good” in Mathematics (19). Some fields simply publish and cite more than others.
Next, how far along is Anna in her career? Junior researchers have a
h-index disadvantage. Their h-index can only be as high as the number of
papers they have published, even if each paper is highly cited. If she
is only 9 years into her career, Anna will not have published as many
papers as someone who has been in the field 35 years.
Furthermore, citations take years to accumulate. The consequence is
that the h-index doesn’t have much discriminatory power for young
scholars, and can’t be used to compare researchers at different stages
of their careers. To compare Anna to a more senior researcher would be
like comparing apples and oranges.
Did you know that Anna also has more than one h-index? Her h-index (and yours) depends on which database you are looking at,
because citation counts differ from database to database. (Which one
should she list on her CV? The highest one, of course. :))
2. The h-index ignores science that isn’t shaped like an article.What if you work in a field that values patents over publications,
like chemistry? Sorry, only articles count toward your h-index. Same
thing goes for software, blog posts, or other types of “non-traditional”
scholarly outputs (and even one you’d consider “traditional”: books).
that come from journal articles, written by other scholars. Your h-index
can’t capture if you’ve had tremendous influence on public policy or in
improving global health outcomes. That doesn’t seem smart.
3. A scholar’s impact can’t be summed up with a single number.
At the scariest times in your career–when you are going up for tenure
or promotion, for instance–do you really want to encourage that? Of
course not. You want your evaluators to see all of the ways you’ve made
an impact in your field. Your contributions are too many and too varied
to be summed up in a single number. Researchers in some fields are rejecting the h-index for this very reason.
measure the right things for your needs. Its particular balance of
quantity versus influence can miss the point of what you care about. For
some people, that might be a single hit paper, popular with both other
scholars and the public. (This article
on the “Big Food” industry and its global health effects is a good
example.) Others might care more about how often their many, rarely
cited papers are used often by practitioners (like those by CG Bremner,
who studied Barrett Syndrome, a lesser known relative of
gastroesophageal reflux disease). When evaluating others, the metrics
you’re using should get at the root of what you’re trying to understand
about their impact.
4. The h-index is dumb when it comes to authorship.
paper. Should their fractional authorship weigh equally with your
single-author paper? The h-index doesn’t take that into consideration.
if that’s the way you indicate lead authorship in your field.) Shouldn’t
citations to that paper weigh more for you than it does your
co-authors, since you had a larger influence on the development of that
So, how should we use the h-index?Many have attempted to fix the h-index weaknesses with various computational models that, for example, reward highly-cited papers, correct for career length, rank authors’ papers against other papers published in the same year and source, or count just the average citations of the most high-impact “core” of an author’s work.
boil down a scientist’s career to a single number that only measures one
type of impact.
measures of how scholarship is recommended, cited, saved, viewed, and
discussed online–are just the solution. Altmetrics measure the influence
of all of a researcher’s outputs, not just their papers. A variety of new altmetrics tools
can help you get a more complete picture of others’ research impact,
beyond the h-index. You can also use these tools to communicate your
own, more complete impact story to others.
Four great reasons to stop caring so much about the h-index - Impactstory blog