∗The research reported on in this paper was supported by the Swiss National Science Foundation under National Research Program No. 28 and the Federal Ministry of Economic Affairs. The commentsof an anonymous referee and the Journal Editor on a previous version of the paper are gratefully acknowledged.
Notes
∗The research reported on in this paper was supported by the Swiss National Science Foundation under National Research Program No. 28 and the Federal Ministry of Economic Affairs. The commentsof an anonymous referee and the Journal Editor on a previous version of the paper are gratefully acknowledged.