Citation Trend Line For PLoS Journals
PLoS One trend lines are quite close to PLoS Computational Biology(CB), now this is very surprising to me and honestly I am very exited about this new development. Recently I was playing with Scopus Journal Analyzer, to find which journal is more suitable for my future manuscript submissions. I am planing to submit my computational study either of these two PLoS journals, although consideration for PLoS One was total financial because of lower author side charge which makes PLoS One (US$1300) more attractive to me, nearly half actually compared to PLoS CB. In past many people suggested that PLoS One is dumping ground for the technically less sound articles, I guess their assumptions seems quite wrong. The current impact factor for PLoS CB is 6.2 which makes it top notch journal for computational biology, while PLoS One is relatively new journal without any official impact factor. Scopus Journal Analyzer provides two very good parameters for journal analysis purpose: first one is Trend Line which is ratio of Total citation received in the given year to Total papers published in the same year; second one is % Not Cited which is percentage of articles published in that year that have never been cited to date. Impact factor vs Trend Line figures for year 2008 are in the same row which means there is loose correlation between these two parameters
Impact factor-:PLoS Biology (13.5) PLoS Genetics (8.7) PLoS CB (6.2)
Trend Line—-PLoS Biology (20.4) PLoS Genetics (10.9) PLoS CB (8.1)
Trend Line—-PLoS Biology (20.4) PLoS Genetics (10.9) PLoS CB (8.1)
Now if we have look on Trend line for 4 PLoS Journals in year 2009
we will find that 4 PLoS journals are segmented in 2 distinct classes: PLoS Biology and PLoS Genetics in one class with trend line values 54.40 and 56.75
while PLoS One and PLoS CB in another class with with Trend Line values 7.75 and 9.31.
Which means PLoS One is equally promising and productive as PLoS CB irrespective of very higher no of articles published in PLoS One. This is more clear if we run across % Not Cited figures,
For example in year 2008 % Not Cited are: PLoS CB (70.06) PLoS One (69.86) PLoS Genetics (67.72) PLoS Biology (59.17), which means irrespective of journal’s impact factor majority of articles are not cited. Even in open access journal impact factor is irrelevant as minority of articles are collecting majority of citations .
Apart from specific figures, PLoS One’s growth and popularity are phenomenal, looks like it will overshadow many journals in its range. I am not sure why people are getting more attracted to lower priced PLoS One, resulting more submissions, for example I will prefer to submit in PLoS One as I am sure it’s impact factor (or quality or what ever you love) is going to be same as PLoS CB or may be much more. It will be interesting to see the number of papers submitted directly to PLoS One and those transferred from other PLoS journals.
Cons: This is a simple comparison, far from being statistically sound.
28 Responses to “Citation Trend Line For PLoS Journals”
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Citation Trend Line For PLoS Journals: PLoS One trend lines are quite close to PLoS Computational Biology(CB), n.. http://tinyurl.com/daysdz
I had a look at the scopus data and I don’t think you can trust the numbers for the current year. I don’t know how often these are updated but you can see for example that PLoS ONE has fewer number of articles in the database so far (112) as expected from the previous year (total year=2737)
PLoS Pathogens for example does not appear to have data for the current year.
More importantly I think this trend line measure tends to give more weight to journals that publish a lot of papers. Try putting PNAS on the same graph for example. Its the total number of citations received by the journal that year (not specifically to the articles of one year) over the number of papers published in one of the years. So you can’t really compare PLoS ONE with the other PLoS Journals in this way
Yes I agree with the fact data in Scopus is not uniform or let say not complete, but not bad either, I agree with the fact trend lines could be biased to journals that publish a lot of papers because it illustrates the total number of citations each journal received (regardless of the publication date of the cited document) in a given year, divided by the total number of documents published in that year, but if we look the trend line with % Not Cited Parameter it definitely gives a clear picture
Probably a nicer number to get is the number of citations from 2008 to papers in 2007. This avoids the problems I mentioned. This number does say that PLoS one is getting more or less the same number of citations per paper than PLoS Comp. and both have about half of PLoS Bio. So I think you are right, PLoS ONE might be get an impact factor similar to PLoS Comp Bio.
@Pedro – curious. Scopus does list an appropriate number of PLoS ONE articles for 2009 (819 articles, which is too low, but understandable with an indexing lag time) but only lists 112 in the analytics engine (which implies their analytics lag their actual data by about a couple of months).
I tried to predict the impact factor of PLoS ONE based on current data. There were 1167 articles published in 2007. These had 3259 citations in 2008. We don’t the full results in already for 2009 but I looked at a few cases and you can usually guess that these will be around 1.2 times the number of citations in 2008 so approximately 3900. These would give PLoS ONE a first impact factor of 6.
I agree with Pedro calculation about possible impact factor of 6 something for PLoS One (around same as PLoS CB ), which is also reflected with Scopus 2009 trends (although data is incomplete).
Also as Pedro suggested “tends to give more weight to journals that publish a lot of papers” but lets not forget this is also affected with time line of journals, older journals will have more better trend line which means PLoS One is certainly doing better
So, do we use IF or not? Or do we just use with the journals we want?
Ok, I re-did the analysis with the correct formula. Also, I noticed that Scopus has multiple entries per articles for some journals. PLoS Comp for example has more than double the number of correct published articles. So, the predicted impact factor for PLoS ONE will be around half of PLoS Comp. Details here in blog post http://pbeltrao.blogspot.com/2009/04/guestimating-plos-one-impact-factor.html
@Paulo well thats interesting questions actually, IF is good measure when it is used for the comparison of the journals, but it is equally bad when it comes to quality of individual research. We definitely need IF or any such thing otherwise it will be never easy to find quality article out of 20,000 journals.
Scopus data for PLoS One is nearly same as ISI. as u can see PLoS One 2007- 1,168(Scopus)1,229(ISI)
PLoS One 2008- 2,745(Scopus)2,760(ISI)
PLoS One Total- 4,869(Scopus)4,962(ISI)
If we use any sort of journal-level metric, we best not use ISIs IF, because it just plainly sucks. Isn’t Scimago ranking PLoS One, yet? Wouldn’t we all fail students who use averages on such obviously non-normally distributed data (or reject any paper for that matter)?
Actually I raised a different kind of question but it unknowingly it became IF game, I just wanted to suggest that PLoS One is getting more attractive and it may overshadow many journals in PLoS family.
Actually I think IF is a decent measure to compare journals even if the citations per paper is not normally distributed. All journals have the same distribution so this number of citations per article is a fair measure. What is not fair is estimate the value of single articles from the IF of the journal where it is was published.
I agree also that we should not decide what articles to read based on IFs of journals but instead based on article level measures but …. we generally don’t have these in place yet.
For that purpose I used Scopus data and Scimago ranking is based on same data and same parameters. Scimago dont rank PLoS One yet
is reading about citation trend lines for #PLoS journals. http://www.abhishek-tiwari.com/2009/04/citationtrend-line-for-plos-journals.html
The Trend Line is a stupid measure because of two reasons:
1) there is no time limit on the citation count: a journal that published 20 years already, has papers from 20 years to be cited. A journal that publishes since 2 years has papers from 2 years that can be cited. Now guess what? The first journal will probably receive more citations, thus – by trend – have a higher Trend Line. Generally speaking, looking at yearly citation counts from journals reveals that most journal have an exponential growth in citations.
2) Does an increased Trend Lin mean the journal receives more citations? Not necessary – it could be that the number of papers published dropped significantly.
Thanks for sharing your thoughts, I guess during discussion I also mentioned above two points: bias due to time line and no of article. Trend line should be observed as trends, particularly how it changing and certainly it’s not a quantifier for the quality of journal, but it does reflect growth of journal.
@pedro: interesting statement that calculating e.g. the median would not change journal rank as compared to arithmetic mean. Conjecture or have you tested that? I’m not sure one way or another, hence, I’d be really interested in such a comparison.
@Bjorn , assuming that the distribution of citations per article will have a similar log normal distribution for most journals I think that is correct. I think the ranking can change but not drastically so. I looked at 10 journals from the same publisher (Nature) from the same year (2007) and the citation information from Scopus (all citations since publication). The correlation between average and median values was 0.96 for these 10 journals.
I hope it was a permanent trend #openknowledge in journals http://tinyurl.com/daysdz
Confessions of a Scopus user…Plos Journal and Journal A.
http://bit.ly/IR4t3
A very interesting comment on this topic…
http://www.plos.org/cms/node/28
Hi people. I just created a poll for the estimate of the first PloS ONE impact factor.
please give your guess at
http://andrew.cmu.edu/user/minlix/poll_plosone.html
thanks