This study was written while I was a doctoral student in the Graduier tenkolleg Finanz-und Gutermiirkte at the University of Mannheim; it has been accepted as a doctoral dissertation in February 1997. I am indebted to my advisors, Professors Axel Borsch-Supan and Martin Hellwig at Mannheim and John Rust at Madison, for their encouragement and for many helpful discussions and comments. At various stages, I benefited from comments on portions of the manu script by, and from discussions with, Thomas Astebro, Charles Calomiris, Timothy Dunne, Frank Gerhard, Annette Kohler, Jens Koke, Stephan...