Brad DeLong is heartened by the response of economists to the question "Because of the American Recovery and Reinvestment Act of 2009, the U.S. unemployment rate was lower at the end of 2010 than it would have been without the stimulus bill":

Effects of the 2009 Recovery Act: Heartening News About What Economists Think--Although Caroline Hoxby and Ed Lazear Do Go All-in for Team Republican..., by Brad DeLong: The University of Chicago's IGM Forum: Poll Results | IGM Forum: Question A: Because of the American Recovery and Reinvestment Act of 2009, the U.S. unemployment rate was lower at the end of 2010 than it would have been without the stimulus bill. At the time, back at the start of 2009, arguments that the Recovery Act would not push the unemployment rate down over the two years after its enactment took one of three lines: Unemployment is really not cyclical but structural, so whatever boost to spending it might generate would show up in higher prices and wages as businesses trying to satisfy demand bid against each other for a fixed pool of non-zero-marginal-product workers. Government purchases must be financed by issuing government debt, and debt issues would push up interest rates and so would discourage private investment spending. Government purchases must be financed by issuing government debt, and the future taxes needed to amortize the extra debt would frighten businesses and investors, so we would see equity prices tank as this fear would discourage private investment. None of those things happened. And that is why the Chicago panel agrees 80%-4% with the statement that the Recovery Act the unemployment rate in 2010 below what it would otherwise have been. And in this context it is worth noting that the two members who want to go on record agreeing with the Republican Party line and disagreeing with the statement appear to do so very carefully... Caroline Hoxby and Ed Lazear, both of Stanford [disagree]. Note that Hoxby appears to be evaluating a different statement--that the ARRA was worth doing--rather than the question asked--that the ARRA reduced the unemployment rate in 2010 below what it would otherwise have been. ... And note that Lazear's comments--"the estimates [of the Recovery Act's effects] are varied and the highest are based on ex-ante models, not experience-based data. The upper bound estimate is low"--appear to justify the position that he is uncertain about the truth of the statement, not that he disagrees with the statement. From one perspective, this is quite heartening: 183 years after John Stuart Mill and Jean-Baptiste Say agreed that Say's Law applies in the long run but not in the short business-cycle run, 4 years after what John Quiggin calls its zombie-like rising from the grave, the claim that increases in government purchases must by the metaphysical necessity of the case--no matter what happens to asset or commodity prices--crowd out an equal and opposite amount of private spending appears to be dead. And staked. Again. To Be Continued...

I don't know that we've learned one important lesson about the use of fiscal policy to attenuate the effects of a downturn. For the most part, even economists who supported fiscal policy as an option insisted that we try monetary policy first and give it a chance to work. Monetary policy alone, we were told, would likely get the job done. And in the unlikely case that it didn't, we could then turn to fiscal policy for help.

That was the wrong advice (and I get annoyed when people who insisted that we wait pat themselves on the back over their support of things like infrastructure spending). By the time we realized that monetary policy would help, but wouldn't be enough to turn things around by itself, it was very late in the game to be applying fiscal policy. Fiscal policy still had an impact, but had it been put in place much earlier -- before problems had a chance to worsen and gel making them harder to overcome -- it would have been much more successful.

When this happens again, we need to to use both monetary and fiscal policy tools to full effect instead of trying one policy, realizing it's not enough, and then turning to the other. But it's not at all clear we've learned this lesson (and, to refine it a bit, we need to get help to state and local governments immediately -- the failure to effectively backfill the budget problems at the state and local level was a big mistake).

Let me emphasize that I'm not saying fiscal policy did not work -- see the following from Jeff Frankel -- only that it could have been much more effective if we hadn't waited so long to put the policies into place:

... The full force of the fiscal stimulus package began to go into effect in the second quarter of 2009, with the NBER officially designating the end of the recession as having come in June of that year. Real GDP growth turned positive in the third quarter, but slowed again in late 2010 and early 2011, which coincides with the beginning of the withdrawal of the Obama administration’s fiscal stimulus.

Other economic indicators, such as interest-rate spreads and the rate of job loss, also turned around in early 2009. ... Again, such data do not demonstrate that Obama’s policies yielded an immediate payoff. In addition to the lags in policies’ effects, many other factors influence the economy every month, making it difficult to disentangle the true causes underlying particular outcomes.

Given that difficulty, the right way to assess whether the fiscal stimulus enacted in January 2009 had a positive impact is to start with common sense. When the government spends $800 billion on such things as highway construction, salaries for teachers and policemen who were about to be laid off, and so on, it has an effect. Workers who otherwise would not have a job now have one, and may spend some of their income on goods and services produced by other people, creating a multiplier effect.

Those who claim that this spending does not boost income and employment (or that it causes harm) apparently believe that as soon as a teacher is laid off, a new job is created somewhere else in the economy, or even that the same teacher finds a new job right away. Neither can be true, not with unemployment so high and the average spell of unemployment much longer than usual. ...

Economists’ more sophisticated forecasting models also show that the fiscal stimulus had an important positive effect... Allowing for a wide range of uncertainty, the CBO estimates that the stimulus added 1.5-3.5% to GDP by the fourth quarter, relative to where it otherwise would have been. The boost to 2010 GDP, when the peak effect of the stimulus kicked in, was roughly twice as great.

Of course, econometric models do not much interest most of the public. A turnaround needs to be visible to the naked eye to impress voters. Given this, one can only wonder why basic charts, such as the 2008-2009 “V” shape in growth and employment, have not been used – and reused – to make the case.