The treasury dept keeps the average duration around 5 years, and paying less than an interest of 1% per year. debt is currently about 80% of GDP. so interest payment is less than 1% of GDP. although 30 year debt at less than 3% is very very cheap treasury is unwilling to borrow at the long end of the curve, fearing higher short term interest cost. instead they bet on rolling over short term debt year after year.
long term borrowing cost is around 6%. it will add 4% of GDP to deficit each year, or about 800 billion each year, or about $8000 for each household.
