Disco_Volante said:
I have to ask this again...
If federal debt is NOT floating rate, that means the interest paid on debt will be the same rate. only the Yield rate changes on the secondary market between traders as the price of the bond rises and falls. So changes in interest rates only affect new issuances, or bonds trading between people in the secondary market. the 18 trillion of government debt....the interest rate is already set for that batch.
So in essence, the price of a bond changes in the secondary market, but the original coupon rate paid by the borrower is the same. So I don't understand how the government's interest payments would rise unless the 18 trillion of debt was all floating rate..... what am I missing?
The part that you are missing is the average duration of the total debt.
http://www.investopedia.com/terms/d/duration.asp
What that means, is how long, on average is the debt committed for.
As two extreme examples: Suppose two different ways of financing the debt at opposite extremes, 30 year bonds verse 4 week T bills.
If all of the debt was financed as 30 year bonds, then changes in the fed funds rate would not matter as much, since the interest payments would be locked in for 30 years. At the end of 30 years, the bonds would have to be paid off or rolled over with new borrowing. The disadvantage of locking in such a long term rate is that the interest rate would be higher. Today a 30 year bond yields about 3%.
If the debt was financed with 4 week T bills, then the annualized interest rate would be much less, at only 0.20% annualized, meaning that if you could keep rolling over the debt at that rate, you would save 2.8% per year .
The problem with having all of the debt in 4 week T Bills is that the rate is not locked in and can change when the debt needs to be rolled over (pay off the maturing borrowing with new borrowing). That is where the problem is.
The average duration on the US debt is some where around 4 to 7 years. In the recent past the duration was down to three years. (I found that for June 2014 the average duration was 68 months, so a little over 5.5 years).
So the problem is that as interest rates rise, and the old debt has to be rolled over with new debt, the interest rate on that new debt is going up.
The interest rate on the debt is somewhere around 2.5% now and the debt is 18 trillion, so if rates keep going up, every quarter point in additional average rate is another 45 billion in interest that adds to the debt, since the United States is running in the red.
If rate went back to a more historical 5% for long rate (or higher), that would be 2.5% higher in interest and add another 450 billion in interest payments, plus whatever the budget was typically short now, would probably make the yearly deficit over $1 trillion, forever.