This prefix denotes a research program that titles a Duranton and Puga paper analyzing sharing, matching, and learning mechanisms of urban agglomeration. Decision analyst Ronald Howard created a unit that uses this prefix to measure a type of risk. Robert Lucas claimed Keynesian economics lacked principles whose name begins with this prefix. A branch of economics named for this prefix was expanded by John Hicks’s book Value and (-5[1])Capital. “Foundations” named for this prefix study agents’ behavior in the context of a whole economy. A branch of economics with this prefix is applied to evaluate a society’s well-being in welfare economics. For 10 points, name this prefix that names a branch of economics studying the decisions of firms and individuals. ■END■ (10[1])