This is aWorking Paper and the author(s) would welcome any comments on the present text Citations should refer to a Working Paper of the International Monetary Fund, mentioning the author(s), and the date of issuance. The views expressed are those of the author(s) and do not necessarily represent those of the Fund.

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We are grateful to Robert M. Stern for helpful comments on an earlier draft of this paper. Financial assistance was provided by the Ford Foundation in support of a program of research in trade policy at The University of Michigan.