Simplicity and Risk

I introduce and test for preference for simplicity in choice under risk. I characterize the theory axiomatically, and derive its properties and unique predictions relative to canonical models. By designing and running theoretically motivated experiments, I document that people value simplicity in ways not fully captured by existing models that study risk premia in financial markets. Participants' risk premia increase as complexity increases, holding moments fixed; their dominance violations increase in complexity; their behavior is predicted by simplicity's characterizing axiom; and their complexity aversion is heterogeneous in cognitive ability. None of expected utility theory, cumulative prospect theory, prospect theory, rational inattention, sparsity, salience, or probability weighting that differs by number of outcomes fully capture the experimental findings. I generalize the underlying theory to additionally capture broader measures of complexity, including obfuscation, computation, and language effects.