This paper investigates the nature and the presence of bubbles in financial markets. Are bubbles consistent with rationality? If they are, do they, like Ponzi games, require the presence of new players forever? Do they imply impossible events in finite time, such as negative prices? Do they need...

The standard model of optimal growth, interpreted as a model of a market economy with infinitely long-lived agents, does not allow separation of the savings decisions of agents from the investment decisions of firms. Investment is essentially passive: the "one good" assumption leads to a...

At a minimum, they suggest that policies may need to become more aggressive, both ex-ante and ex-post, with a rebalancing of the roles of monetary, fiscal and financial policies. In particular, while low neutral rates decrease the scope for using monetary policy, they increase the scope for...

Debt sustainability is fundamentally a probabilistic concept: Debt is rarely sustainable with probability one. We propose an index of external debt sustainability that reflects this uncertainty. Namely we construct the index as the probability that, at the current exchange rate, net external...

In the 1970s, large increases in the price of oil were associated with sharp decreases in output and large increases in inflation. In the 2000s, and at least until the end of 2007, even larger increases in the price of oil were associated with much milder movements in output and inflation. Using...

We explore empirically models of aggregate fluctuations with two basic ingredients: agents form anticipations about the future based on noisy sources of information; these anticipations affect spending and output in the short run. Our objective is to separate fluctuations due to actual changes...

We characterize the macroeconomic performance of a set of industrialized economies in the aftermath of the oil price shocks of the 1970s and of the last decade, focusing on the differences across episodes. We examine four different hypotheses for the mild effects on inflation and economic...

This paper investigates the relation between growth forecast errors and planned fiscal consolidation during the crisis. We find that, in advanced economies, stronger planned fiscal consolidation has been associated with lower growth than expected, with the relation being particularly strong,...

We answer the question posed by the title by specifying and estimating a simple dynamic model of prices, wages, and short-run and long-run inflation expectations. The estimated model allows us to analyze the direct and indirect effects of product-market and labor-market shocks on prices and...

In a collaborative project with ten central banks, we have investigated the causes of the post-pandemic global inflation, building on our earlier work for the United States. Globally, as in the United States, pandemic-era inflation was due primarily to supply disruptions and sharp increases in...