Still, the exercise Crawford has undertaken is an important reminder—as the United States continues to prosecute its wars against ISIS, al-Qaeda, and the Taliban—of the hidden price of conflict, whether measured in interest accrued by 2020 or veterans’ medical bills in 2050. The costs of war can linger long after the fighting ends. (Crawford chose not to calculate the economic toll of the wars for other countries, and she and her colleagues have estimated the staggering human costs of the conflicts in separate reports.)

I asked Crawford why the Bush administration had decided to break with historical precedent and pay for its wars the way it had. “We are a society that’s much more comfortable with debt culturally than in the past,” she said. “We saw individuals take on more mortgage debt, more credit-card debt.”

Sometimes—when, for instance, buying a house or paying for a child’s education—taking on debt is a prudent investment, she added. But that doesn’t apply to the way America has funded its fight against terrorism: “It’s like my car: I need it to get to work. I might get into a little bit of debt to have this thing. But it’s as if I keep borrowing and borrowing and borrowing, and I never pay, so I never really get rid of that debt. And then I’m going to pass that debt on to my child. What we’ve done with this deficit financing is we’ve passed the debt on to future generations.”

The government is acting as if this debt can be passed on indefinitely, she said, but it could actually constrain the government in the future from providing basic services and responding to emergencies. As Alan Viard, an economist who served in the Bush administration, once put it, “When you borrow to pay for the war, you feel it less. But if you do borrow, it may be future needs you’re sacrificing. There’s always a sacrifice.”

The Bush administration’s decision may also have stemmed from “hubris,” Crawford said. The mentality in the administration in the years immediately after 9/11 was, “We can go kick their butts, kill them, remake their societies, hopefully have other people pay for it, remake the Middle East, promote democracy, people will be safer, and we’re going to give you a tax break!”

“If we hadn’t had such low interest rates, and Congress had moved, for example, to raise taxes instead of cut them, the public would have paid attention to these wars in a different way,” Crawford added.

Today’s debates over government spending typically revolve around whether a particular government program is wasteful or appropriate or effective, not whether the nation’s leaders have made the right tradeoffs between defense and non-defense spending. “We have this sense of scarcity and distress and outrage about the deficit,” Crawford said, “but we don’t connect the dots to war spending or military spending in general,” which accounts for more than 50 percent of federal discretionary spending.