""Nationwide provider statistics aren’t readily available, but multiple large studies show a consistent ratio of anesthesia providers with about 35% of anesthetics provided by physicians in solo practice, about 55% provided by CRNAs with anesthesiologist direction, and about 10% provided by CRNAs in solo practice.""
There is your 10%. So that means 90% of CRNAs work with MDAs. But that even more proves what I said about factors that do not matter.
Even though CRNAs can work independently of MDAs, since 90% do NOT.... then the whole issue of independent practice when talking about MDA/AA groups is comparing apples to oranges.