“As of the end of December, 71 percent of borrowers with pay-option loans were electing to make less than full interest payments.”
I read this to mean that IN DECEMBER, 71% didn’t pay the whole monthly payment. I believe SDEngineer is on the right track, with the subtle difference that the 71% isn’t necessarily repeat offenders, but just a 1 month instance.
The remaining 20% would be people who missed a payment in an earlier month but paid in December. Of course, I would hands down presume that the majority of the 71% who didn’t pay in December are probably repeat offenders.