Originally Posted by BrotherBock
Do you have a link to these results?
There's a podcast or two on Basic Brewing Radio with the BYO/BBR collaborative results.
There are other podcasts with John Palmer talking about this issue as well.
John Palmer started saying in 2008 that he "made a mistake" in his book (called How to Brew) when he gave formulas and utilization formulas that considered wort gravity as a factor in hops utilization. He now says it has no affect, and most of the other science minded brewers think the same thing.
John did tell me back in 2010 when we were having a beer and chatting that "break material may have an impact on utilization" but there isn't any formula to correlate that. I didn't ask more questions, but I'm sure he expounded more on that. I just don't remember much more than that, to be honest.
If you google a bit, you may find the newer thinking on hops utilization, the impact of wort gravity on IBUs, and the hows and whys.