---- Acknowledgements -----
We are grateful to Rudi Bachmann, Susanto Basu, John Cochrane, Daniel Cooper, Lutz Kilian, Matthew Shapiro, and seminar participants at the University of Michigan for helpful comments and discussions. We thank John Fernald for providing us with his TFP data. All remaining errors are our own. Barsky acknowledges support from the Russell Sage Foundation as a visiting scholar, and Sims acknowledges the support of theHorace H. Rackham School of Graduate Studies at the University of Michigan. The views expressed herein are those of the author(s) and do not necessarily reflect the views of the National Bureau of Economic Research.