Most people might think that it would be because the U.S. government would have to pay much more interest on the national debt.  And yes, if the average rate of interest on U.S. government debt rose to just 6 percent (and it has actually been much higher in the past), the federal government would be paying out about a trillion dollars a year just in interest on the national debt.  But that isn't it.  Nor does the primary reason have to do with the fact that rapidly rising interest rates would impose massive losses on bond investors. At this point, it is being projected that if U.S. bond yields rise by an average of 3 percentage points, it will cause investors to lose a trillion dollars.  Yes, that is a 1 with 12 zeroes after it.