Six years ago this month, Congress passed and President Obama signed the $819 billion American Recovery and Reinvestment Act (ARRA), a package of short-term spending hikes and tax cuts better known as “the stimulus.” ARRA wasn’t Washington’s first attempt to borrow-and-spend its way out of the then-deepening recession; George W. Bush approved a $167 billion stimulus the previous February. Nor was ARRA the last or largest attempt: the December 2010 federal budget deal was really a $917 billion stimulus. All told, Washington hurled at least $2.5 trillion at the recession through programs like “Cash for Clunkers,” three different jobs bills, and the homebuyer tax credit.[1]

Despite those trillions, the American economy was still stagnant in early 2013 when the “budget sequester” clamped down on federal spending. Politicians and commentators predicted doom, saying such “austerity” would rekindle the recession.[2] Paul Krugman lectured the “fools” in Washington that more deficit spending was needed, not less.[3] Some 350 academics and activists grimly warned that “budget cuts in a deep slump lead only to a deeper slump.”[4] They repeated those predictions a few months later when Congress reinstituted the 26-week limit on federal unemployment benefit funds and a feud between Congress and the White House shut down part of the federal government.

 But instead of disaster, the American economy started to improve. Since the summer of 2013, gross domestic product has grown at an average rate of 3 percent—a solid if not spectacular clip and the best run in nearly a decade. Once Washington politicians stopped “fixing” the economy, it finally began to heal.

So if a stagnant economy suddenly improves while government spending shrinks, what’s a Keynesian to do?

Keynesianism—at least today’s version—is the belief that economic growth comes from government profligacy. John Maynard Keynes, the brilliant theoretical economist whose ideas are borrowed—often half-digested—by today’s Keynesians, believed that in bad economic times government should increase spending and cut taxes in order to boost demand for goods and services. That, in turn, would create jobs, and the new workers would spend their paychecks and create still more demand and jobs. (Keynes also believed that in good times government should cut spending and raise taxes to moderate the economy and pay off debt. Today’s Keynesians remember only the “raise taxes” part of that idea.)

But the real economy operates much differently than in Keynes’ theory. For instance, between 1929 and 1932, President Herbert Hoover doubled real federal spending and financed the increase with debt, yet the Great Depression grew worse.

The flaw in Keynes’ theory is that it takes a lot of government spending and tax cuts to stimulate the economy even a tiny little bit. One reason for this is all the time needed for stimulus to start working: government has to write and adopt the legislation, then let contracts, then get the money flowing and circulating. Those delays dissipate the fiscal “push” that Keynesians want to create. Another reason is that when government debt increases, taxpayers cut their own spending because they realize that one day they’ll have to pay off the government’s bills.[5] A third reason is that government buys goods that are very different from what people and companies buy, especially in today’s world. Back in Keynes’ day, an unemployed factory worker may have been able to transition easily to a government road crew, but he’d have a much harder time becoming today’s transit worker or compliance officer. So a temporary increase in government demand doesn’t spark much sustained increase in broader demand.

Some of the most important empirical research on the failure of fiscal stimulus comes from University of California, Berkeley economist Christina Romer.[6] She finds that it did little to help the United States out of any of the recessions of the 20^th century, including the Depression. “What ends recessions,” she and husband David explained in one paper, is monetary stimulus—the lowering of interest rates and other finance-boosting actions, like President Franklin Roosevelt’s halving of the gold exchange rate during the Great Depression[7] or the many Federal Reserve efforts of recent years.

Interestingly, Romer chaired President Obama’s Council of Economic Advisers in 2009 and helped design the stimulus. Why would she champion a policy that her own research indicates doesn’t work? Perhaps she believed her stimulus would have much better results than past efforts. Or perhaps she thought there were other benefits from the legislation and that “stimulus” was just useful political cover, following Rahm Emanuel’s advice to not let a crisis go to waste. Or perhaps she was just overwhelmed by the demands of politicians eager to spend money they didn’t have; she left the administration the following year.

Hopefully, the current spurt of economic growth will prove enduring. The federal government has roughly doubled its debt, to $18.1 trillion, since it first began fighting the recession in 2008. American taxpayers now have a lot more bills to pay and, with Social Security and Medicare insolvency looming and soaring costs for Medicaid and the 2009 health care law, more bills are on the way. It will be hard to pay those bills if Americans are struggling to find jobs.