A former advisor to George Bush has written a piece in the New York Times that finally asks the question that conservatives have wanted someone with influence to ask of the incoming administration:

Is Government Spending Too Easy an Answer?

HOW MUCH BANG FOR EACH BUCK? Economics textbooks, including Mr. Samuelson’s and my own more recent contribution, teach that each dollar of government spending can increase the nation’s gross domestic product by more than a dollar. When higher government spending increases G.D.P., consumers respond to the extra income they earn by spending more themselves. Higher consumer spending expands aggregate demand further, raising the G.D.P. yet again. And so on. This positive feedback loop is called the multiplier effect.

In practice, however, the multiplier for government spending is not very large. The best evidence comes from a recent study by Valerie A. Ramey, an economist at the University of California, San Diego. Based on the United States’ historical record, Professor Ramey estimates that each dollar of government spending increases the G.D.P. by only 1.4 dollars. So, by doing the math, we find that when the G.D.P. expands, less than a third of the increase takes the form of private consumption and investment. Most is for what the government has ordered, which raises the next question.

WILL THE EXTRA SPENDING BE ON THINGS WE NEED? If you hire your neighbor for $100 to dig a hole in your backyard and then fill it up, and he hires you to do the same in his yard, the government statisticians report that things are improving. The economy has created two jobs, and the G.D.P. rises by $200. But it is unlikely that, having wasted all that time digging and filling, either of you is better off.

People don’t usually spend their money buying things they don’t want or need, so for private transactions, this kind of inefficient spending is not much of a problem. But the same cannot always be said of the government. If the stimulus package takes the form of bridges to nowhere, a result could be economic expansion as measured by standard statistics but little increase in economic well-being.

Mankiw's point is simple;

A recent study by Christina D. Romer and David H. Romer, then economists at the University of California, Berkeley, finds that a dollar of tax cuts raises the G.D.P. by about $3. According to the Romers, the multiplier for tax cuts is more than twice what Professor Ramey finds for spending increases.

Why this is so remains a puzzle. One can easily conjecture about what the textbook theory leaves out, but it will take more research to sort things out. And whether these results based on historical data apply to our current extraordinary circumstances is open to debate.

Christina Romer, incidentally, has been chosen as the chairwoman of the Council of Economic Advisers in the new administration. Perhaps this fact helps explain why, according to recent reports, tax cuts will be a larger piece of the Obama recovery plan than was previously expected.

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All these questions should give Congress pause as it considers whether to increase spending to stimulate the economy. But don’t expect such qualms to stop the juggernaut. The prevailing orthodoxy among the nation’s elite holds that increased government spending is the right medicine for what ails the economy.