Review and Synthesis S U P P O R T I N G I N F O R M A T I O N Additional Supporting Information may be found in the online version of this article: Appendix S1 References of articles analyzed in table 2 and full data matrix. Please note: Wiley-Blackwell are not responsible for the content or functionality of any supporting materials supplied Are specialists at risk? 863 by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. Editor, Vojtech Novotny Manuscript received 28 January 2009 First decision made 10 March 2009 Manuscript accepted 11 May 2009 2009 Blackwell Publishing Ltd/CNRS