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.

Public investment represents a non-negligible fraction of total public expenditures. Yet, theoretical studies of the effects of public spending when the economy is stuck in a liquidity trap invariably assume that government expenditures are entirely wasteful. In this paper, we consider a...