We develop a theory of endogenous uncertainty in which the ability of investors to learn about firm-level fundamentals is impaired during financial crises. At the same time, higher uncertainty reinforces financial distress. Through this two-way feedback loop, a temporary financial shock can cause a persistent reduction in risky lending, output, and employment that coincides with increased uncertainty, default rates, credit spreads, and disagreement among forecasters. We embed our mechanism into standard real business cycle and New-Keynesian models and show how it generates endogenous and internally persistent processes for the efficiency and labour wedges.

We analyze a dynamic credit market where banks choose lending standards, modeled as costly effort to screen out bad borrowers. Tighter standards worsen the borrower pool, increasing banks’ incentives to employ tight standards in the future. This dynamic complementarity in lending standards can amplify and prolong downturns, decreasing lending and increasing credit spreads. Because lending standards have negative externalities, the market can converge to a steady state with inefficiently tight lending standards. We discuss the role of optimal policy to avoid this outcome as well as the impact of balance sheet costs on lending standards.

We show that in a broad class of menu cost models, the first-order dynamics of aggregate inflation in response to arbitrary shocks to aggregate costs are nearly the same as in Calvo models with suitably chosen Calvo adjustment frequencies. We first prove that the canonical menu cost model is first-order equivalent to a mixture of two time-dependent models, which reflect the extensive and intensive margins of price adjustment. We then show numerically that in any plausible parameterization, this mixture is well approximated by a single Calvo model. This close numerical fit carries over to other standard specifications of menu cost models. Thus, for shocks that are not too large, the Phillips curve for a menu cost model looks like the New Keynesian Phillips curve, but with a higher slope.

We generalize the traditional, static Keynesian cross by deriving an intertemporal Keynesian cross for the dynamic output response to government spending and taxes in microfounded general equilibrium models. Intertemporal marginal propensities to consume (iMPCs) are sufficient statistics for this response, with fiscal multipliers depending only on the interaction between iMPCs and public deficits. We provide empirical estimates of iMPCs and argue that they are inconsistent with representative agent or two-agent models but can be matched by certain heterogeneous agent models. Models that match empirical iMPCs imply larger and more persistent output responses to deficit-financed fiscal policy, with cumulative spending multipliers above 1.