Authoring journal articles is not only enhancing to one's CV (the old "publish or perish" cliche), it is required by residency review committees as evidence of "scholarly activity" in training programs. Maybe it's good for attracting referrals too.
Without too much difficulty, I have collected some interesting information about the number of authors per paper in several specialties.
First noted in 1993 by a paper in Acta Radiologica and a letter in the BMJ, the number of authors per paper has risen dramatically over the years.
A study of 12 radiology journals found the number of authors per paper doubled from 2.2 in 1966 to 4.4 in 1991.
A review of Neurosurgery and the Journal of Neurosurgery spanned 50 years. the average went from 1.8 authors per article in 1945 to 4.6 authors in 1995.
Of note, the two articles above were each written by a single author.
Three psychiatrists from Dartmouth analyzed original scientific articles in the four of the most prestigious journals in the United States—Archives of Internal Medicine, Annals of Internal Medicine, Journal of the American Medical Association, and the New England Journal of Medicine—from 1980 to 2000. They found the mean number of authors per paper increased from 4.5 to 6.9.
The same is true for two plastic surgery journals, which saw the average number of authors go from 1.4 to 4.0 and 1.7 to 4.2 in the 50 years from 1955 to 2005. The number of single-author papers went from 78% to 3% in one journal and 51% to 8% another.
In orthopedics, a review of the American and British versions of the Journal of Bone and Joint Surgery for the 60 years from 1949 to 2009 showed an increase of authors per paper from 1.6 to 5.1.
An even greater rise in the number of authors took place in two leading thoracic surgery journals. For the Journal of Thoracic and Cardiovascular Surgery the increase was 1.4 in 1936 to 7.5 2006 and for Annals of Thoracic Surgery it was 3.1 in 1966 to 6.8 in 2006.
Where will it end?
Skeptical Scalpel is a recently retired surgeon and was a surgical department chairman and residency program director for many years. He is board-certified in general surgery and a surgical sub-specialty and has re-certified in both several times. For the last two years, he has been blogging at SkepticalScalpel.blogspot.com and tweeting as @SkepticScalpel. His blog averages over 900 page views per day, and he has over 6000 followers on Twitter.