We investigate the size of the multiplier at the ZLB in a New keynesian model. It ranges from around -0.25 to +1.5, depending on the extent to which government spending is productive, substitutable or not for private consumption.

We study the effectiveness of public investment in stimulating an economy stuck in a liquidity trap. We do so in the context of a tractable new-Keynesian economy in which a fraction of government spending increases the stock of public capital subject to a time-to-build constraint. Public...