The claim is substantiated by the largest study accomplished on US health care and administration ever to date. It was authored by researchers at Harvard Medical School and, I believe, published in 2006.
Though I did make an error I wish to clarify.
Private insurance carriers do not spend 30 per cent on over head. The number averages closer to 12 to 17 per cent depending on the carrier.
The study appeared in a prestigous, academic and peer-reviewed journal -International Journal of Health Services.
It is too long to post the entire study, and I am not in the habit of doing your homework for you.