In 2008, the federal government made $253 billion in net interest payments on debt that was $5 trillion at the end of fiscal year 2007, for a 5 percent average interest rate on the debt. The government made only $240 billion in interest payments in 2016, although the debt had more than doubled to $13.1 trillion at the end of fiscal year 2015, for a 1.8 percent average interest rate.
http://www.aei.org/publication/the-coming-challenge-of-servicing-our-national-debt/
