If you are thinking about your research group and are wondering on whether to include more people you better read this.
Ralph Kenna from the University of Coventry and Bertrand Berche from the University of Nancy (France) have analyzed the correlation between quality and research group size for different areas, based on data collected for the UK’s 2008 Research Assessment Exercise (RAE). Their findings are very interesting. While one could think that more people would get better results together, it seems that this is not true indefinitely. There is a linear relation between group size and quality of the scientific results, and they correlate until reaching a breaking point, which is different for different areas. In experimental physics the breaking point is 25 people while in theoretical physics is 13. Once reached the breaking point, if you keep increasing the group size, quality does not increase anymore, and the trend flatten out.
The analysis shows that there is also a lower critical mass calculated as a minimum of 2 persons for theorists and 13 for experimentalists to guarantee an healthy scientific outcome.
This is probably something to keep in mind when deciding about future strategies. If you are interested in reading the original article you can find it here: http://arxiv.org/abs/1006.0928