Tempora Mutantur: In Search of a New Testament for NEG

The aim of this article is twofold. First, we present an integrative framework that encompasses a large share of existing neg models. This framework allows us to discuss the fundamental assumptions and the key results that hold throughout a broad class of models. We argue that progress within the straight-jacket of that framework, though potentially important, is unlikely to produce path-breaking new insights. Second, we suggest that there are potentially large payoffs to stepping outside of the established framework and to extend the neg approach into various directions that have to date received only scant attention. Heterogeneity, cities, transportation, and calibration are avenues along which neg needs to make progress in the future.