It's NASCAR not Nascar! I mentioned it
here. Let's say you were drafted in 1940. As a private, you would have earned 50$ a month. While in the States, and in England, you probably would have spent that money while on pass. Then you get shipped off to Italy or France or some other combat zone where your opportunities to spend your wages probably totaled around zero. Suddenly the war is over, you are demobilized and you're sent home. Now you have the GI Bill. So you decide to go to medical school or law school or tech school. After graduating, you open your own practice and hire a couple of nurses and secretaries, or legal assistants, or whatever. You also buy a newly constructed home in the suburbs with your VA benefits to raise the large family you're about to start. Between 1944 and 1973, up to one third of the population follows a similar path, since the draft made them eligible for the program. Businesses are founded, neighborhoods are constructed, and families are started -- incomes rise, commerce grows, and the tax revenue increases, enabling the government to invest in education, technology (yes, like the internet), the interstate system, and so on.
Fast forward to 2012. Maybe you're a private, or a NCO, or an officer. It doesn't matter. Maybe you use the GI Bill, or Tuition Assistance, or the military's graduate studies program. Most likely, you're a careerist since retention rates are fairly high. So with the exception of the direct payments to your education institution, your education isn't value added to the economy; just your career (and only to a small extent). You don't hire anybody or start a business because the military gives you people to supervise. You might buy a home or rent, but eventually you'll leave your current neighborhood for the next one -- which might be in a foreign community. And when you deploy, you supervise or guard the construction of a new school or outpost. Or two. Or three or four. And to defend these gains invested outside of the country, you might fire a few rounds from your unit's crew served weapons or direct the targeting of a JDAM. Whatever you decide to do, you expend America's wealth abroad, not at home. It's not your fault of course; a well-to-do company makes those missiles, and the military purchases them for a few million dollars, and they're designed to be expended on the battlefield while that company's earnings are divested among its owners (some of whom may be in Congress). And maybe that school you spent a year trying to get started does get off the ground, but how many of those Iraqis and Afghans are going to grow up to start a business or own a home in America? The point is, you don't leave the service and your net economic input into the economy is equal to that of your disposable wages, since your time and energy and resources are generally spent abroad. And you repeat that process two or three or even four times.