We develop a tractable method for augmenting macroeconomic models with autonomous variation in higher‐order beliefs. We use this to accommodate a certain type of waves of optimism and pessimism that can be interpreted as the product of frictional coordination and, unlike the one featured in the news literature, regards the short‐term economic outlook rather than the medium‐ to long‐run prospects. We show that this enrichment provides a parsimonious explanation of salient features of the data; it accounts for a significant fraction of the business‐cycle volatility in estimated models that allow for various competing structural shocks; and it captures a type of fluctuations that have a Keynesian flavor but do not rely on nominal rigidities.

We study optimal policy in an economy where interest rates are low because public debt serves as collateral or buffer stock. Issuing more public debt raises welfare by easing the underlying friction but also reduces the private valuation of this service, raising interest rates. This trade-off shapes the optimal quantity of public debt in the long run, justifies a departure from tax smoothing in the short run, and calls for larger deficits during financial crises. Our analysis illustrates the possible robustness of these insights to different microfoundations and helps clarify when exactly low interest rates represent an opportunity for cheap government borrowing.

We propose a new strategy for dissecting the macroeconomic time series, provide a template for the business-cycle propagation mechanism that best describes the data, and use its properties to appraise models of both the parsimonious and the medium-scale variety. Our findings support the existence of a main business-cycle driver but rule out the following candidates for this role: technology or other shocks that map to TFP movements; news about future productivity; and inflationary demand shocks of the textbook type. Models aimed at accommodating demand-driven cycles without a strict reliance on nominal rigidity appear promising. (JEL C22, E10, E32)