Commitment to the behaviorist approach to utility theory, to the usefulness of mathematics in economic analysis and to equalization of the marginal utility of income as a principle of just taxation brought Irving Fisher and Ragnar Frisch to attempt to measure the marginal utility of income, and led them to collaborate in forming the Econometric Society and sponsoring the establishment of the Cowles Commission, institutions advancing economic theory in connection to mathematics and statistics. To be presented at a symposium at the University of Oslo, December 3, 2019, honoring the 50th anniversary of the award to Ragnar Frisch of the Royal Bank of Sweden Prize in Economic Science in Memory of Alfred Nobel and the 30th anniversary of the awar...