[JamesP]

Here is what I got when I divided cost by GDP. (Average GDP for multi year wars)

Cost GDP
War 2000 Dollars %GDP
1812 1 10.73 9%
Civil 72 81.63 88%
WW2 4,800 1674 287%
Iraq 165 10390 2%

This is the total cost divided by the yearly GDP.

[JamesP]

  

	Cost	GDP
War	Billions	2000 Dollars	%GDP
War of 1812	1	11.73	9%
Civil War	72	81.63	88%
WW2	4,800.00	1674	287%
Iraq	165	10390	2%