Do último artigo de Robert Barro e Charles Redlick:
"For U.S. annual data that include WWII, the estimated multiplier for defense spending is 0.6-0.7 at the median unemployment rate. There is some evidence that this multiplier rises with the extent of economic slack and reaches 1.0 when the unemployment rate is around 12%. Multipliers for non-defense purchases cannot be reliably estimated because of the lack of good instruments. For samples that begin in 1950, increases in average marginal income-tax rates (measured by a newly constructed time series) have a significantly negative effect on real GDP. Increases in taxes seem to reduce real GDP with mainly a one-year lag due to income effects and mostly a two-year lag due to substitution (tax-rate) effects. Since the defense-spending multiplier is typically less than one, greater spending tends to crowd out other components of GDP. The largest effects are on private investment, but non-defense purchases and net exports tend also to fall. The response of private consumer expenditure differs insignificantly from zero. "