Abstract: This paper helps provide foundations for survey-based tracking of well-being. First, we propose a theory in which utility depends on “fundamental aspects” of well-being, measurable with surveys. Second, drawing from psychologists, philosophers, and economists, we compile a comprehensive list of such aspects. Third, to estimate the aspects’ marginal utilities—a necessary input for constructing an individual-level well-being index—we conduct a survey in which ~4,600 U.S. respondents state their preference between pairs of aspect bundles. We estimate high relative marginal utilities not only for traditional happiness and life satisfaction measures, but even more for aspects related to family, health, security, values, and freedoms.