ACL-3International audienceThis paper proposes a regime-dependent model to estimate fiscal multipliers in the US. Output, consumption and investment are assumed to respond to tax and spending changes in a nonlinear manner. Fiscal multipliers are time-varying because their size and sign depend upon the state of the economy (upturns and downturns). Keynesian effects appear essentially during downturns, while anti-Keynesian effects are observed during expansions. Transfer payments contributes to a higher private consumption when they are given to consumers in bad times. Reducing taxes boosts consumption in good times. Investment responds positively to lower taxes during downturns, but negatively in the upturn regime. Our results thus suggest t...