In empirical studies, the data usually don't include all the variables of interest in an economic model. This paper shows the identification of unobserved variables in observations at the population level. When the observables are distinct in each observation, there exists a function mapping...

The focus of this Element is on the idea that choice is hierarchical so that there exists an order of acquisition of durable goods and assets as real incomes increase. Two main approaches to deriving such an order are presented, the so-called Paroush approach and Item Response Theory. An...

Economic models often depend on quantities that are unobservable, either for privacy reasons or because they are difficult to measure. Examples of such variables include human capital (or ability), personal income, unobserved heterogeneity (such as consumer "types"), etc. This situation has...