Some thoughts on Journal Impact Factor
A colleague just e-mailed me to ask me how I felt about journal
impact factor being
such a big part of the Academic Ranking of World Universities - they say that 20% of the
ranking weight comes from # of papers published in Nature and Science.
So what do I think?
I'm really not a big fan of rankings and evaluations in the first
place. This is largely because I feel that evaluations are rarely
objective. For one very specific example, last year at MSU I got
formal evaluations from both of my departments. Starting with the same
underlying data (papers published, students graduated, grants
submitted/awarded, money spent, classes taught, body mass/height
ratio, gender weighting, eye color, miles flown, talks given, liquid
volume of students' tears generated, committees served on, etc.) one
department gave me a "satisfactory/satisfactory/satisfactory" while
the other department gave me an "excellent/excellent/excellent." What
fun! (I don't think the difference was the caliber in departments.)
Did I mention that these rankings helped determine my raise for the
Anyhoo, I find the rating and ranking scheme within departments at MSU
to be largely silly. It's done in an ad hoc manner by untrained
people, and as far as I can tell, is biased against people who are not
willing to sing their own praises. (I brought up the Dunning-Kruger
effect in my last evaluation meeting. Heh.) That's not to say there's
not serious intent -- they are factored into raises, and at least one
other purpose of evaluating assistant professors is so that once you
fire their ass (aka "don't give them tenure") there's a paper trail of
critical evaluations where you explained that they were in trouble.
Metrics are part of the job, though; departments evaluate their
faculty so they can see who, if anyone, needs help or support or
mentoring, and to do this, they rely at least in part on metrics.
Basically, if someone has lots of funding and lots of papers, they're
probably not failing miserably at being a research professor; if
they're grant-poor and paper-poor, they're targets for further
investigation. There are lots of ways to evaluate, but metrics seem
like an inextricable part of it.
Back to the impact factor
Like faculty evaluations, ranking by the impact factor of the
journals that university faculty publish in is an attempt to
predict future performance using current data.
But impact factor is extremely problematic for many reasons. It's
based on citations, which (over the long run) may be an OK measure of
impact, but are subject to many confounding factors, including
field-specific citation patterns. It's an attempt to predict the
success of individual papers on a whole-journal basis, which falls
apart in the face of variable editorial decisions. High-impact
journals are also often read more widely by people than low-impact
journals, which yields a troubling circularity in terms of citation
numbers (you're more likely to cite a paper you've read!) Worse, the
whole system is prone to being gamed in various ways, which is leading
to high rates of retractions for high-impact journals,
as well as outright fraud.
Impact factor is probably a piss-poor proxy for paper impact, in other
If impact factor was just a thing that didn't matter, I wouldn't
worry. The real trouble is that impact factors have real-world effect
- many countries use impact factor of publications as a very strong
weight in funding and promotion decisions. Interestingly, the US is
not terribly heavy handed here - most universities seem pretty
enlightened about considering the whole portfolio of a scientist, at
least anecdotally. But I can name a
dozen countries that care deeply about impact factor for promotions
And apparently impact factor affects university rankings, too!
Taking a step back, it's not clear that any good ranking scheme can
exist, and if it does, we're certainly not using it. All of this is a
big problem if you care about fostering good science.
The conundrum is that many people like rankings, and it seems futile
to argue against measuring and ranking people and
institutions. However, any formalized ranking system can be gamed and
perverted, which ends up sometimes rewarding the wrong kind of people,
and shutting out some of the right kind of people. (The Reed College
position on the US News & World Report ranking system is worth reading
generally, in any ecosystem, the competitive landscape is evolving,
and a sensible measure today may become a lousy measure tomorrow as
the players evolve their strategies; the stricter the rules of
evaluation, and the more entrenched the evaluation system, the less
likely it is to adapt, and the more misranking will result. So
ranking systems need to evolve continuously.
At its heart, this is a scientific management challenge. Rankings and
metrics do pretty explicitly set the landscape of incentives and
competition. If our goal in science is to increase knowledge for the
betterment of mankind, then the challenge for scientific management is
to figure out how to incentive behaviors that trend in that direction
in the long term. If you use bad or outdated metrics, then you
incentivize the wrong kind of behavior, and you waste precious time,
energy, and resources. Complicating this is the management structure
of academic science, which is driven by many things that include
rankings and reputation - concepts that range from precise to fuzzy.
My position on all of this is always changing, but it's pretty clear
that the journal system is kinda dumb and rewards the wrong
behavior. (For the record, I'm actually a big fan of publications, and
I think citations are probably not a terribly bad measure of impact
when measured on papers and individuals, although I'm always happy to
engage in discussions on why I'm wrong.) But the impact factor is
especially horrible. The disproportionate effect that high-IF glamour
mags like Cell, Nature and Science have on our scientific culture is
clearly a bad thing - for example, I'm hearing more and more stories
about editors at these journals warping scientific stories directly or
indirectly to be more press-worthy - and when combined with the
reproducibility crisis I'm really worried about the short-term future
of science. Journal Impact Factor and other simple metrics are
fundamentally problematic and are contributing to the problem, along
with the current peer review culture and a whole host of other
things. (Mike Eisen has written about this a lot; see e.g. this post.)
In the long term I think a much more experimental culture of peer
review and alternative metrics will emerge. But what do we do for now?
How can we change?
I think my main advice to faculty is "lead, follow, or get out of the way."
Unless you're a recognized big shot, or willing to take somewhat
insane gambles with your career, "leading" may not be productive -
following or getting out of the way might be best. But there are a lot
of things you can do here that don't put you at much risk, including:
- be open to a broader career picture when hiring and evaluating
- argue on behalf of alternative metrics in meetings on promotion and
- use sites like Google Scholar to pick out some recent papers to read
in depth when hiring faculty and evaluating grants;
- avoid making (or push back at) cheap shots at people who don't have
a lot of high-impact-factor papers;
- invest in career mentoring that is more nuanced than "try for lots
of C-N-S papers or else" - you'd be surprised how often this is the
main advice assistant professors take away...
- believe in and help junior faculty that seem to have a plan, even if
you don't agree with the plan (or at least leave them alone ;)
What if you are a recognized big shot? Well, there are lots of
things you can do. You are the people who set the tone in the
community and in your department, and it behooves you to think
scientifically about the culture and reward system of science. The
most important thing you can do is think and investigate. What
evidence is there behind the value of peer review? Are you happy with
C-N-S editorial policies, and have you talked to colleagues who get
rejected at the editorial review stage more than you do? Have you
thought about per-article metrics? Do you have any better thoughts on
how to improve the system than 'fund more people', and how would you
effect changes in this direction by recognizing alternate metrics
during tenure and grant review?
The bottom line is that the current evaluation systems are the
creation of scientists, for scientists. It's our responsibility to
critically evaluate them, and perhaps evolve them when they're
inadequate; we shouldn't just complain about how the current system is
broken and wait for someone else to fix it.
Addendum: what would I like to see?
Precisely predicting the future importance of papers is obviously kind
of silly - see this great 1994 paper by Gans and Shepherd on
rejected classics papers, for example -- and is subject to all sorts
of confounding effects. But this is nonetheless what journals are
accustomed to doing: editors at most journals, especially the high
impact factor ones, select papers based on projected impact before
sending them out for review, and/or ask the reviewers to review impact
So I think we should do away with impact review and review for
correctness instead. This is why I'm such a big fan of PLOS One and PeerJ, who purport to do
But then, I get asked, what do we do about selecting out papers to
read? Some (many?) scientists claim that they need the filtering
effect of these selective journals to figure out what they should be
There are a few responses to this.
First, it's fundamentally problematic to outsource your attention to
editors at journals, for reasons mentioned above. There's some
evidence that you're being drawn into a manipulated and high-retraction
environment by doing that, and that should worry you.
But let's say you feel you need something to tell you what to read.
Well, second, this is technologically solvable - that's what search
engines already do. There's a whole industry of search engines that
give great results based on integrating free text search, automatic
content classification, and citation patterns. Google Scholar does a
great job here, for example.
Third, social media (aka "people you know") provides some great
recommendation systems! People who haven't paid much attention to
Twitter or blogging may not have noticed, but in addition to
person-to-person recommendations, there are increasingly good
coming on line. I personally get most of my paper recs from online
outlets (mostly people I follow, but I've found some really smart
people to follow on Twitter!). It's a great solution!
Fourth, if one of the problems is that many journals review for
correctness AND impact together, why not separate them? For example,
couldn't journals like Science or Nature evolve into literature
overlays that highlight papers published in impact-blind journals like
PLOS One or PeerJ? I can imagine a number of ways that this could
work, but if we're so invested in having editors pick papers for us,
why not have them pick papers that have been reviewed for scientific
correctness first, and then elevate them to our attention with their
magic editorial pen?
I don't see too many drawbacks to this vs the current approach, and
many improvements. (Frankly this is where I see most of scientific
literature going, once preprint archives become
So that's where I want and expect to see things going. I don't see
ranking based on predicted impact going away, but I'd like to see it
more reflective of actual impact (and be measured in more diverse
p.s. People looking for citations of high retraction rate, problematic
peer review, and the rest could look at one of my earlier blog posts
on problems with peer review.
I'd be interested in more citations, though!
Syndicated 2014-11-10 23:00:00 from Living in an Ivory Basement