We survey literature on ambiguity with an emphasis on recent applications in macroeconomics and finance. Like risk, ambiguity leads to cautious behavior and uncertainty premia in asset markets. Unlike risk, ambiguity can generate first order welfare losses. As a result, precautionary behavior...

We reinterpret post World War II US economic history using an estimated microfounded model that allows for changes in the monetary/fiscal policy mix. We find that the fiscal authority was the leading authority in the '60s and the '70s. The appointment of Volcker marked a change in the conduct of...

Concave hiring rules imply that firms respond more to bad shocks than to good shocks. They provide a unified explanation for several seemingly unrelated facts about employment growth in macro and micro data. In particular, they generate countercyclical movement in both aggregate conditional...

This paper considers business cycle models with agents who dislike both risk and ambiguity (Knightian uncertainty). Ambiguity aversion is described by recursive multiple priors preferences that capture agents' lack of confidence in probability assessments. While modeling changes in risk...

This paper estimates a business cycle model with endogenous financial asset supply and ambiguity averse investors. Firms' shareholders choose not only production and investment, but also capital structure and payout policy subject to financial frictions. An increase in uncertainty about profits...

In the 1970s, U.S. asset markets witnessed (i) a 25% dip in the ratio of aggregate household wealth relative to GDP and (ii) negative comovement of house and stock prices that drove a 20% portfolio shift out of equity into real estate. This study uses an overlapping generations model with...

In modern monetary economies, most payments are made with inside money provided by payment intermediaries. This paper studies interest rate dynamics when payment intermediaries value short bonds as collateral to back inside money. We estimate intermediary Euler equations that relate the short...

This paper uses new household survey data to study expectation formation during the recent housing boom in Germany. The cross section of forecasts depends on only two household characteristics: location and tenure. The average household in a region responds to local conditions but underpredicts...

This paper studies how managers plan under uncertainty. In a new survey panel on German manufacturing firms, we show that uncertainty reflects change: Planning incorporates higher subjective uncertainty about future sales growth when the firm has just experienced unusual growth, and more so if...

Why did the real interest rate decline and the equity premium increase over the last 30 years? This paper assesses the role of uncertainty and credit market frictions. We quantify a model with heterogeneous households using data on asset prices and macro aggregates, as well as on households'...