The AP’s Donna Cassata is reporting today on a study commissioned by the Senate Armed Services Committee, which purports to calculate the costs of the U.S. military presence overseas. This is a hot topic, but it isn’t exactly a new one. Americans have long been frustrated by inequitable burden sharing, with many of our wealthy allies spending a fraction of what we do on defense. On Monday, Cato published a new infographic on the subject to coincide with tax day (see below).

Unfortunately, the committee’s estimate that the permanent stationing of U.S. troops overseas costs us $10 billion each year is too low–in all likelihood, much too low. I have not yet had a chance to read the entire report, but the DoD’s own estimate of overseas military costs includes the costs of personnel, and is more than twice that amount, $20.9 billion (see p. 207 in the latest budget submission). Even the DoD’s figure, however, understates the true cost of our commitments to defend other countries that can and should defend themselves, because it doesn’t fully account for the additional force structure that is required to maintain a presence many thousands of miles away from the United States. If the U.S. military operated chiefly in the Western Hemisphere, with regular expeditionary operations far afield, we could safely have fewer people on active duty, and mobilize a large and well-trained reserve for genuine emergencies. This smaller military would require ships and planes to take them where they were needed, when they were needed, but not as many planes and ships as we have today. And no report can actually assess the costs and risks when and if our security commitments compel us to become embroiled in a distant war that does not engage vital U.S. interests.

Other studies have attempted to assess all of the costs of these various global commitments, and the estimates vary widely. Graham Fuller and Ian Lesser of the RAND Corporation, for example, estimated in 1997 that the U.S. military presence in the Persian Gulf cost between $30 and $60 billion per year. A more recent study by Mark Delucchi and James Murphy estimated costs between $47 and $98 billion. Several of us at Cato have been compiling these estimates, and coming up with our own, as part of a comprehensive study of the costs of our global military presence. We will publish our key findings when they become available.

In the meantime, this much is clear: our security commitments, many of them holdovers from the Cold War, induce other countries to spend less than they could on their own defense. And they compel Americans to spend more than we should.