Some additional Googling seems to have found some other independent studies:
http://hiqnews.megafoundation.org/John_Scoville_Paper.htm
http://www.abelard.org/burt/burt-ie.asp
I'm curious what sort of population your work draws from. The results above showed that IQ follows a normal distribution until about 140; other papers I've read indicate that IQ correlates with life outcomes until an IQ of about 140, and then appears completely uncorrelated. If you're studying workplace performance, I wouldn't be surprised if a good fraction of high-IQ people simply aren't in the workplace. (See eg. Christopher Langan.)