The ultimate impact of an expenditure of X is greater than X. This is known as the [link|http://www.cnmi-guide.com/info/essays/economics/33.html|multiplier effect]. It's based on the marginal propensity to consume -- the amount of money that's spent rather than saved or otherwise withdrawn from circulation. Given an MPS of 0.8, the impact of $40b would be $800b. This starts to get significant.

The other side of the coin is directed spending. We've currently seen "pump priming" in the sense of reducing interest rates to stimulate investment...but the investment hasn't happened. The other tack (the first is called "monetary policy", it influences the money supply) is direct government expenditure directed at specific projects. This is Keynsian "fiscal policy", and has the advantage of specifying exactly where the economic activity will occur (or disadvantage if you're opposed to direct government meddling with the economy). In a situation in which the private sector won't step in and start increasing activity, such a leadership role may have advantages.

Peace.