From David Leonhardt's February 16 New York Times analysis:

Imagine if, one year ago, Congress had passed a stimulus bill that really worked.

Let's say this bill had started spending money within a matter of weeks and had rapidly helped the economy. Let's also imagine it was large enough to have had a huge impact on jobs - employing something like two million people who would otherwise be unemployed right now.

If that had happened, what would the economy look like today?

Well, it would look almost exactly as it does now. Because those nice descriptions of the stimulus that I just gave aren't hypothetical. They are descriptions of the actual bill.

Just look at the outside evaluations of the stimulus. Perhaps the best-known economic research firms are IHS Global Insight, Macroeconomic Advisers and Moody's Economy.com. They all estimate that the bill has added 1.6 million to 1.8 million jobs so far and that its ultimate impact will be roughly 2.5 million jobs. The Congressional Budget Office, an independent agency, considers these estimates to be conservative.

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Because the economy is still a long way from being healthy, members of Congress are now debating another, smaller stimulus bill. (They're calling it a “jobs bill,” seeing stimulus as a dirty word.) The logical thing to do would be to examine what worked and what didn't in last year's bill.

But that's not what is happening. Instead, the debate is largely disconnected from the huge stimulus experiment we just ran. Why? As Senator Scott Brown of Massachusetts, the newest member of Congress, said, in a nice summary of the misperceptions, the stimulus might have saved some jobs, but it “didn't create one new job.”

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Given what people have been saying about a successful stimulus bill, just imagine what they'll say about one that doesn't accomplish much.