I had a bone-marrow transplant in late 2012.
Over the next year, the Hospital and Insurance companies went round and round, churning out bills and checks.
In one case, the insurance company needed some information from the hospital to process the claim. SNAFU at the hospital left the insurance company without the info for about six months.
Soooo, the hospital sent the bill to a collection agency, which started sending me letters demanding payment. I was, therefore, among the 35%.
The next month, the hospital sent the info to the insurance company, the insurance company cut a check, and the collections agency sent me a "never mind" letter.
So, I never really had any overdue debt, but I would have counted under the methodology of this article as part of the 35%.
Which leads me to wonder what fraction of the 35% might have had debts referred mistakenly to collection agencies....