* Gerarden: Harvard Kennedy School, 79 John F. Kennedy St., Cambridge, MA 02138 (e-mail: [email protected]); Newell: Nicholas School of the Environment, Duke University, 140 Science Dr., 101 Gross Hall, Durham, NC 27708 (email: [email protected]); Stavins: Harvard Kennedy School, 79 John F. Kennedy St., Cambridge, MA 02138 (e-mail: [email protected]). This paper draws in p...

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