Economic Perspectives, Federal Reserve Bank of Chicago, (2007), vol. 31 n.3, pp.33-43. A more complete version is available as NBER Working Paper no. 13200
Review of Economic Dynamics (2006),
vol.9, n.2, pp. 211-223.
An
earlier
version (with some typos) is available as Working Paper, Federal Reserve Bank of Chicago, 2006 n.2.