Greater effectiveness of singles.....
Most of the discussion on "more effective hooking with singles, and less lost fish" has come from the spoon and plug fishermen, and it is true in that case. There is more than sufficient data to argue that point. However, I know of no studies, other than someone's opinions, to argue the same case for flies. I think that we have carried this idea over to flies as "gospel".
Only way to prove the point is with a statistically valid study.
But since many of us fish with small dry flies and small nymphs, I doubt if there would be much interest, other than salmon and steelhead fishers.... and we are a minority.