On the KQED interview I did on the federal budget, I made the following statement:
I'm actually an advocate of having the defense budget be the defense budget, not the offense budget. And most of what the government spends now is either directly for wars against other countries that have never attacked us or to prepare for wars against other countries that are unlikely to attack us. And so I would like to see the U.S. government pull out of all the bases in the world, and I think we could cut the defense budget, which is really an offense budget, by approximately $500 billion a year.
I made this $500 billion estimate based on the idea that over half of the approximately $800 billion spent on defense ($700 billion for DoD plus a lot of Department of Energy spending plus a lot of of Veterans Affairs plus much of CIA spending) is for offense. See my recent review of Chris Preble's book for some numbers from 2007.
Later, I wanted to find studies that would back up or refute my estimate and I can't find any. Years ago Earl Ravenal of Cato did such a study but I haven't seen one in the last decade or so. It seems that that would be very valuable and that a think tank such as the Cato Institute or the Independent Institute would have done one. But I can't find such a study. Does anyone know of one? Links would be valuable too.