This paper analyzes the sustainability of fixed exchange rates by extending the Barro-Gordon framework to a fully dynamic context in which the level of a state variable (in this case debt) determines the payoffs available to the government at each point of time.

We argue that allowing for the possibility of a self-fulfilling panic helps understand several features of the recent Mexican crisis. Self-fulfilling expectations became decisive in generating a panic only after the government ran down gross reserves and ran up short-term dollar debt. We present...