The biggest problem is that in spite of the name, Treasury has no money, so they sell 20 years to buy 30 years .Then sell 10 years to buy 20 years , sell 2 years to buy 10 years ..   then because 2 years becomes due very fast, they have to sell 30 years. Fundamental problem, nobody believes US or rather USD is worth more than toilet paper in 30 years .  They are basically like a person snowballing His credit card bills, at certain levels, it is unsustainable, so banks sells the debt to someone else. See why catches the ball. The bank will continue to bankroll a person as long as he pays the minimun because once they stop, the illusion stops too. So they reduce the person credit limits. Most central banks and funds are buying less US bonds, basically they are reducing US credit li