He is credited with developing the first learning-by-doing model, and he co-authored Existence of a Competitive Equilibrium for a Competitive Economy with Gerard Debreu.  
With Herve Raynaud, this man wrote about the axioms of diversity, symmetry, and positive responsiveness.  He is credited with developing the first learning-by-doing model, and he co-authored Existence of a Competitive Equilibrium for a Competitive Economy with Gerard Debreu.  A type of risk aversion is named after Pratt and this man, and he developed a result similar to the Gibbard-Satterthwaite theorem which relies on independence of irrelevant alternatives and non-dictatorship.  For 10 points, name this author of Social Choice and Individual Values, who stated that some voting systems cannot fairly rank candidates in his namesake "Impossibility Theorem."
With Herve Raynaud, this man wrote about the axioms of diversity, symmetry, and positive responsiveness.  
Kenneth Arrow