Abstract
A nudge is a paternalistic government intervention that attempts to improve choices by changing the framing of a decision problem. We propose a welfare-theoretic foundation for nudging similar in spirit to the classical revealed preference approach, by investigating a framework in which preferences and mistakes of an agent can be elicited from her choices under different frames. We provide characterizations of the classes of behavioral models in which the information required for nudging can or cannot be deduced from choice data.