  This paper provides the first historical analysis of the relationship between
collaboration and scientific impact, using three indicators of collaboration
(number of authors, number of addresses, and number of countries) and including
articles published between 1900 and 2011. The results demonstrate that an
increase in the number of authors leads to an increase in impact--from the
beginning of the last century onwards--and that this is not simply due to
self-citations. A similar trend is also observed for the number of addresses
and number of countries represented in the byline of an article. However, the
constant inflation of collaboration since 1900 has resulted in diminishing
citation returns: larger and more diverse (in terms of institutional and
country affiliation) teams are necessary to realize higher impact. The paper
concludes with a discussion of the potential causes of the impact gain in
citations of collaborative papers.
