Its from a book, Code Blue: Inside Americas Medical Industrial Complex, by Mike Magee. The author is a Doctor and distinguished medical academic and past hospital executive.
The book contains many references, but it's dense. I thought admin overhead tended to go to 15% because of ACA provisions of 85% spending requirement on direct care? I would likely have to do a fair bit of digging to compare how the scope is defined exactly vs an ACA definition. Makes for something of a perverse incentive if the companies want/need to route additional absolute dollars into their service depts - but I don't know how much it actually gets bent in that direction.