Several months ago I wrote a post about the number of references cited in a typical JGR-ES article. In the meantime, I’ve found some purpose for this analysis beyond my curiosity — a recent paper by Fox et al. found that an increasing the number of references cited is correlated with higher citations. This is easy to believe — more cited references leads to more visible in citation databases and searches.
To extend my previous work looking at the JGR-ES reference section stats, I want to look at the size of reference sections in length restricted journals — specifically in Geology from GSA and Geophysical Research Letters from AGU.
First, Geology: On September 26th I downloaded 9915 Geology paper records from the Web of Science (Geology papers from 1975 to the present). A histogram of number of cited references in a given paper (for all 9915 papers, regardless of age) is shown below:
The mean is 26 cited references. Thirty papers cite no references — most seem to be meeting reports or other similar manuscripts. One (cool looking) paper has 108 cited references (9x the mean, wow!).
The plot below shows the temporal trends in this data:
Red is median, blue box denote the 1st and 3rd percentage breaks, and the whisker denotes the range (with a few outliers as red ‘+’ marks).
In 1975, the mean number of references cited in a Geology paper was 18. In 2015, the mean number of references cited was 29. In Geology, the cited references section grows another reference every 4 years… not much.
Now on to GRL — on October 9th I downloaded 33,391 GRL records from the Web of Science (1974 to the present). Below is the histogram of reference count for all of these records.
The mean for GRL is 21 (compared to 26 for Geology). The maximum from GRL is paper with 135 cited references (compared to a max of 108 in Geology).
Now for the temporal trends in GRL:
In 1974, the mean number of cited references was 12 (similar to Geology’s 18 cited references in 1975). In 2015 the mean number of cited references in a GRL paper was 35 (compared to Geology’s 2015 mean of 29 cited refs). So for GRL, references grow by 1 reference every 2 years (twice as fast as Geology). However, note that the GRL reference section growth seems to be most pronounced in the last 5-10 years (see above).
Update 11/2/2016: Andrew Ashton reminded me that GRL relaxed their page limit sometime within this window of time… I can’t find the editorial or announcement to pinpoint the date, but I will keep looking….