It is well known that the long-run viability of a fixed exchange rate regime imposes constraints on monetary policy. This paper shows that, in a model with forward-looking agents, short-run viability imposes a fiscal constraint. When policy change, which destroys long-run viability, also violates the fiscal constraint, collapse is instantaneous. Delayed predictable collapse requires satisfaction of the fiscal constraint.

It is well known that the long-run viability of a fixed exchange rate regime imposes constraints on monetary policy. This paper shows that, in a model with forward-looking agents, short-run viability imposes a fiscal constraint. When policy change, which destroys long-run viability, also violates the fiscal constraint, collapse is instantaneous. Delayed predictable collapse requires satisfaction of the fiscal constraint.

ical) and to self-fulfilling currency crisis, respectively. Research stressing the former approach was pioneered by Krugman (1979) and Flood and Garber (1984). According to this line of research, the failure of governments to adopt domestic monetary and fiscal policies consistent with their stated exchange rate targets leads to a gradual diminution of reserves and eventually a stock adjustment that depletes reserves suddenly in one attack (Sachs, Tornell, and Velasco, 1996, page 47). The result is either a devaluation of the exchange rate or a switch to floating. Subsequent work of this genre has specified a number of other channels, in addition to that involving inconsistent and unsustainable monetary and fiscal policies, that can precipitate an attack: 1. Inconsistency between external and internal objectives. The stances of monetary and fiscal policies may be consistent with the authorities' exchange rate target, but domestic economic indicators (such as the unemployment rate) may be inconsistent with internal balance, resulting in pressures on the authorities to relax macroeconomic policies. Private agents, aware of this inconsistency, perceive an opportunity for profits from a currency devaluation and precipitate an attack. 2. Contagion effects. Prior to an attack on another currency (say that of country B), the market may view a country's (say, country A's) exchange rate as consistent with economic fundamentals and, thus, sustainable.

This paper reviews the literature on financial crises focusing on three specific aspects. First, what are the main factors explaining financial crises? Since many theories on the sources of financial crises highlight the importance of sharp fluctuations in asset and credit markets, the paper briefly reviews theoretical and empirical studies on developments in these markets around financial crises. Second, what are the major types of financial crises? The paper focuses on the main theoretical and empirical explanations of four types of financial crises—currency crises, sudden stops, debt crises, and banking crises—and presents a survey of the literature that attempts to identify these episodes. Third, what are the real and financial sector implications of crises? The paper briefly reviews the short- and medium-run implications of crises for the real economy and financial sector. It concludes with a summary of the main lessons from the literature and future research directions.

This paper reviews the theoretical and empirical literature on the effectiveness of fiscal policy. The focus is on the size of fiscal multipliers, and on the possibility that multipliers can turn negative (i.e., that fiscal contractions can be expansionary). The paper concludes that fiscal multipliers are overwhelmingly positive but small. However, there is some evidence of negative fiscal multipliers.