What is the optimal number of researchers for social science research?

Many studies have found that co-authored research is more highly cited than single author research. This finding is policy relevant as it indicates that encouraging co-authored research will tend to maximise citation impact. Nevertheless, whilst the citation impact of research increase as the number of authors increases in the sciences, the extent to which this occurs in the social sciences is unknown. In response, this study investigates the average citation level of articles with one to four authors published in 1995, 1998, 2001, 2004 and 2007 in 19 social science disciplines. The results suggest that whilst having at least two authors gives a substantial citation impact advantage in all social science disciplines, additional authors are beneficial in some disciplines but not in others.