How Small is Small? Non-linearities in Heterogeneous Agent Models

Abstract

In plausibly calibrated heterogeneous-agent models, marginal propensities to consume (MPCs) are highly non-linear in wealth, falling sharply away from borrowing constraints. As a result, the aggregate consumption response to a fiscal transfer is strongly concave in its size: larger transfers shift households out of high-MPC regions, dampening the consumption response. Across partial- and general-equilibrium settings, linear methods substantially overstate the effects of fiscal stimulus at empirically relevant sizes. Local methods of any order are unlikely to be reliable in settings where a failure of Ricardian equivalence from high MPCs is important.