Model fees ... and what does this mean?

I gave a talk today at the CFA Society of Philadelphia on GIPS(R) 2010 (Global Investment Performance Standards) and mentioned that effective January 1, 2010, compliant firms must disclose, when reporting net-of-fee returns, if model or actual fees are used. Earlier this year I mentioned that there is no definition of "model fees" in the glossary but that I suspect it means highest actual fee. Well, someone asked if it's possible to use "average fee."

While I suspect not, given the lack of clarity here I'm reluctant to give a definitive "no!" With no explanation as to what "model fee" means, some might suspect they have some leeway.

I will e-mail the GIPS help desk to try to gain some clarity.