In the literature on currency and banking crises it has become the standard procedure to distinguish pure currency crises, pure banking crises and combined (“twin”) currency and banking crises. We show theoretically and empirically that a similar differentiation should be chosen with regard to currency and debt crises. Twin currency and debt crises differ from both pure currency and pure debt crises in their determinants, course of events, and economic consequences. We find that each type of crises has a unique set of macroeconomic causes. We also identify internal contagion and selection bias effects, which may lead to biased empirical estimates if twin crises are not treated as a specific type of crises. Such a separation allows in significantly improving the efficiency of early warning systems especially for debt and twin crises.

While currency crises are typically considered to be painful and costly events, a closer look reveals that economic developments after a speculative attack differ considerably. Monetary authorities can play a central role in determining the economic course and costs of currency crises. They have to decide whether to defend or not to defend the domestic currency giving rise to three different types of crises: (i) an immediate depreciation if the central bank does not intervene and either (ii) a successful defense or (iii) an unsuccessful defense in the case of an intervention. We find that a central bank has two options to mitigate the costs of speculative attacks, namely an immediate depreciation and a successful defense. If a central bank intervenes she might be able to stabilize the exchange rate only temporarily and risks to ultimately fail facing the worst of the three scenarios with the highest economic costs.