Which is Worse,Tax Fluctuations or Spending Fluctuations?

Acknowledgements: Many thanks to Michael Abramowicz, Bruce Ackerman, Anne Alstott, Alan Auerbach, Ian Ayres, Robert Bartlett, Lily Batchelder, Mitch Berman, Neil Buchanan, Terry Chorvat, Mechele Dickerson, Michael Doran,Elizabeth Garrett, Mark Gergen, James Hines, Jonathan Klick, Kinch Hoekstra, Calvin Johnson, AmyKapczynski, Louis Kaplow, Michael Knoll, Kyle Logue, Dan Markovits, Ed McCaffery, Melissa Murray,Leslie Papke, Bob Peroni, Eric Rakowski, Chris Sanchirico, Alvaro Santos, Larry Sager, Jason Schultz, Darien Shanske, Dan Shaviro, Kirk…