Wait. It gets worse. A new report from the International Monetary Fund shows that the kind of recession we’ve had, a recession caused by a financial crisis, often leads to long-term damage to a country’s growth prospects. “The path of output tends to be depressed substantially and persistently following banking crises.”

The same report, however, suggests that this isn’t inevitable: “We find that a stronger short-term fiscal policy response”  by which they mean a temporary increase in government spending  “is significantly associated with smaller medium-term output losses.”

So we should be doing much more than we are to promote economic recovery, not just because it would reduce our current pain, but also because it would improve our long-run prospects.

But can we afford to do more  to provide more aid to beleaguered state governments and the unemployed, to spend more on infrastructure, to provide tax credits to employers who create jobs? Yes, we can.

The conventional wisdom is that trying to help the economy now produces short-term gain at the expense of long-term pain. But as I’ve just pointed out, from the point of view of the nation as a whole that’s not at all how it works. The slump is doing long-term damage to our economy and society, and mitigating that slump will lead to a better future.

What is true is that spending more on recovery and reconstruction would worsen the government’s own fiscal position. But even there, conventional wisdom greatly overstates the case. The true fiscal costs of supporting the economy are surprisingly small.

You see, spending money now means a stronger economy, both in the short run and in the long run. And a stronger economy means more revenues, which offset a large fraction of the upfront cost. Back-of-the-envelope calculations suggest that the offset falls short of 100 percent, so that fiscal stimulus isn’t a complete free lunch. But it costs far less than you’d think from listening to what passes for informed discussion.

Look, I know more stimulus is a hard sell politically. But it’s urgently needed. The question shouldn’t be whether we can afford to do more to promote recovery. It should be whether we can afford not to. And the answer is no.