This coming year, I am told that Thomson Reuters will release section-specific Journal Impact Factors for JGR. I want to give the community a heads-up on where we stand.
If your institution has a subscription to Thomson Reuter’s Web of Science, then it is not a difficult to do a search for “Journal of Geophysical Research Space Physics” in the “Publication Name” field for specific years (one at a time) and get the citation numbers for a Journal Impact Factor specific for JGR-Space Physics.
I just did this and here are the results:
Unofficial JIF for JGR-Space Physics:
Number of items published in 2014: 760
Number of items published in 2013: 711
Cites in 2015 to items published in 2014: 1808
Cites in 2015 to items published in 2013: 2077
My estimate of the 2015 JGR-Space Impact Factor = 3885 / 1471 = 2.64
Hmm. This is well below the JGR-all sections JIF of 3.3 reported by Thomson Reuters. When I do this same search but with “Journal of Geophysical Research *” for the publication name, then I get a value of 3.20. This is close but a bit lower than the Thomson Reuters value. This is expected because I did not remove Editorials, Prefaces, and other items from the list of “papers”, which presumably have few if any citations and which presumably Thomson Reuters removes from the JIF calculation. So, perhaps the JGR-Space Physics value that I just calculated should be up by a tenth or two, but most likely it is still below 3.0.
I gathered the numbers for the 5-year Impact Factor, and for 2015, JGR-Space Physics has 2.76. Better than the 2-year JIF above, as expected because the journal has such a long cited half-life. With the correction to the denominator, this value is approaching 3.0, but again, probably not all the way up to it.
I was a nerd about it and pulled values back to 2002, when JGR went digital. This gives me 2-year JIF scores back to 2004 and 5-year JIF scores back to 2007. With my simple method, there has only been one 2-year JIF for JGR-Space Physics above 3.0, in 2012. The lowest is in 2004, which I calculate to be 1.89, but I am not sure that I trust the citation numbers for 2002; they are noticeably lower than other years and it is the year of the “switch.” So, removing this, then the next lowest year is 2007, with 2.25. Most years are between 2.5 and 2.7.
What does this mean? It means that this is the “level” for the JIF of JGR-Space Physics. Adding in the “Immediacy Index” values (cites in the same year as publication), which are usually between 0.6 and 0.8, and the total number of citations in the first two years of a paper’s life is, on average, between 6 and 6.5.
Note that the number of papers without a citation at all is very low. After 2 years, it is already down to just a few percent. Nearly all papers are cited at least once. In fact, total citations for the average paper increases almost linearly for the first ~8 years or so, as seen here:
I’d say that’s pretty good.
In fact, it is a big reason why I am not afraid of the coming official release of a JIF specific to JGR-Space Physics and its expected value of below 3.0. This journal’s papers have longevity, accumulating citations well past anyone’s journal metric calculations. People have published good papers in this journal, and present-day researchers continue to cite those studies. We take a while to absorb a result and build on it. The JIF is useful as a journal metric, but it is not the whole story.