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Wikipedia notes several recent changes to the debt ceiling. Increases in the debt ceiling allow the Treasury to borrow more money and increase the national debt to a level higher than previously allowed by law.

August 5, 1997 5,950 +450 Pub.L. 105–33
June 11, 2002 6,400 [26] +450 Pub.L. 107–199
May 27, 2003 7,384 +984 Pub.L. 108–24
November 16, 2004 8,184 [26] +800 Pub.L. 108–415
March 20, 2006 8,965 [27] +781 Pub.L. 109–182 
September 29, 2007 9,815 +850 Pub.L. 110–91 
June 5, 2008 10,615 +800 Pub.L. 110–289
October 3, 2008 11,315 [28] +700 Pub.L. 110–343
February 17, 2009 12,104 [29] +789 Pub.L. 111–5 
December 24, 2009 12,394 +290 Pub.L. 111–123 
February 12, 2010 14,294 +1,900 Pub.L. 111–139 
January 30, 2012 16,394 +2,100
May 19, 2013 16,700

How much in interest payments since 2002, has the increase in borrowing from the previous debt ceiling of $5,950 billion to the new debt ceiling of $16,700 billion, cost the US?

Note: Only count additional interest payments on the debt from 2002-present due to the increased borrowing limit authorized by Congress, not all interest payments since 2002.

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    I may get you a more complete answer later, but since 2010 we've arguably been saving money by borrowing because the real interest rates are negative. – Avi Oct 16 '13 at 3:42
  • @Avi, good point. Inflation needs to be factored into the equation. The changes in debt between 2010 and present are marginal though (only $2.4 trillion), does that make a large enough dent in the additional interest payments when the rate was much higher (before the 2007 crash)? – user1873 Oct 16 '13 at 4:41
  • I'm afraid I'd have to check. – Avi Oct 16 '13 at 5:34
  • As I understand this question it boils down to "what is the difference between current interest payments on government borrowing compared with 2002?" Is that a fair summary? – DJClayworth Oct 31 '13 at 14:48
  • @DJClayworth, not exactly. What is the cumulative difference in interest payments from the additional debt above the 1997-2002 debt ceiling of $5.950t? I am only interested in the additional interest paid on debt above the previous debt ceiling, not the interest in the entire debt, nor a single year comparison. – user1873 Oct 31 '13 at 15:10
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Changes in the debt ceiling have no direct effect on the amount of interest paid. Only when the permissions granted by the debt ceiling are utilized to create actual debt does interest become payable. Therefore we will estimate the increase in interest payments since 2002 due to increases in the amount of borrowing.

Changes in interest paid depends on two things - changes in interest rates and changes in amount borrowed. We will try to factor out the first by considering the fraction of the debt for any year that is above the 2002 level. it is assumed that the same fraction of the interest paid is due to the debt level above the 2002 level. Dollar amounts are in billions.

Year   Debt   % above 2002     interest     due to post-2002 debt
2002   $6,228       0%           $332               $0
2003   $6,783       8%           $318              $25
2004   $7,379      15%           $321              $48
2005   $7,933      21%           $352              $74
2006   $8,507      27%           $405             $109
2007   $9,008      31%           $429             $133
2008  $10,025      39%           $451             $175
2009  $11,910      48%           $383             $184
2010  $13,562      54%           $414             $224

I'll leave adding up the final column as an exercise for the reader.

A fairly large factor we have had to leave out is inflation (which reduces the impact of the interest and the debt) . We also have not cross-referenced this with GDP changes, or with increases in government income. Both generally increase the governments ability to pay interest on the debt.

NOTES

  1. Debt figures are from Wikipedia.
  2. Interest figures are from the Treasury
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  • +1 this is what i was looking for. You mght want to reconsider the GDP comment about ability to "service the debt". It gives the impression that the US intends to repay the principal. CBO projections for the last 10+ years have estimated that the defict would be eliminated (hasn't happened since Clinton) and for the next 10+ years we are estimated to keep increasing the deficit. – user1873 Oct 31 '13 at 17:44
  • You should definitely recalculate with inflation, particularly given how low interest rates have become relative to inflation recently. – Avi Oct 31 '13 at 22:48
  • The figures are referenced. Please feel free to use them. – DJClayworth Nov 1 '13 at 14:22
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I took the figures referenced by DJClayworth and updated up to 2014 numbers and included inflation. enter image description here (if someone can tell me how to paste excel as pre-formatted text I'm happy to paste the actual values, but the headers were off and this works for my purposes)

In actual dollar terms the US has paid a cumulative $1,993B in interest for solely post-2002 debt. Adjusted for inflation this number is $1,103B.

Also adjusted for inflation, however, the interest the US pays on its debt has actually dropped 11% since 2002 unless I botched the math.

I would be eager to see someone take change in GDP/government revenue over this time period to see, adjusted for inflation, what % of the budget goes to interest now as opposed to 2002.

Debt source

Interest source

Inflation source

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  • Export from Excel as fixed-width text (rather than CSV). Then paste here. Select the whole block and either hit Ctrl+K or click the Code button. That should work, although I don't use Excel and can't test it at the moment. – Brythan Jun 8 '18 at 20:37

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