At the May run rate, annual U.S. interest costs are about $1.6 trillion—nearly the size of the entire federal budget in 1997

Based on May's pace, the U.S. federal government is paying roughly $1.6 trillion a year in interest alone—about what the entire federal budget totaled as recently as 1997. As more low-yield debt rolls off and is refinanced at higher rates, the annual bill is poised to climb above $2 trillion, approaching 40% of federal tax revenue.