Are astronomical papers with more authors cited more?

Following my previous study of paper length vs. number of citations in astronomy (Stanek 2008), some colleagues expressed an interest in knowing if any correlation exists between citations and the number of authors on an astronomical paper. At least naively, one would expect papers with more authors to be cited more. I test this expectation with the same sample of papers as analyzed in Stanek (2008), selecting all (∼ 30, 000) refereed papers from A&A, AJ, ApJ and MNRAS published between 2000 and 2004. These particular years were chosen so that the papers analyzed would not be too “fresh”, but number of authors and length of each article could be obtained via ADS. I find that indeed papers with more authors published in these four major astronomy journals are on average cited more, but only weakly so: roughly, the number of citations doubles with ten-fold increase in the number of authors. While the median number of citations for a 2 author paper is 17, the median number of citations to a paper with 10 to 20 authors is 32. However, I find that most papers are written by a small number of authors, with a mode of 2 authors and a median of 3 authors, and 92% of all papers written have fewer than 10 authors. Perhaps surprisingly, I also find that papers with more authors are not longer than papers with fewer authors, in fact a median number of 8 to 10 pages per paper holds for any number of authors. For the same sample of papers, a median number of citations per paper grew from 15 in June 2008 (Stanek 2008) to 19 in November 2009. Unlike Stanek (2008), I do not conclude with any career advice, semi-humorous or otherwise.