I think the the study he is referencing is the 1998 paper by Schmidt & Hunter. We studied it in business school. I couldn't find an actual copy of the paper but these two articles have abstracts of the findings: http://psycnet.apa.org/index.cfm?fa=buy.optionToBuy&id=1... http://www.onetest.com.au/awms/Upload/documents/whitepapers/...

Schmidt, F.L. & Hunter, J.E. (1998) The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings,” Psychological Bulletin,

Thanks. I had read the conclusion I mentioned in monographs about psychology I was reading for other research interests, and I'm glad you cited a key review article. I found the article's full text

http://mavweb.mnsu.edu/howard/Schmidt%20and%20Hunter%201998%...

via Google Scholar.