Heterogeneity in consumer behaviour creates differences in demand responses, which may create problems with aggregation across consumers. If aggregation problems exist, results from estimation based on aggregate data may prove difficult to interpret. Using estimation results from micro data to...

Some well-known correlations between R&D and performance are given a somewhat new interpretation in this paper. I present an alternative model of knowledge accumulation, with some interesting and desirable properties. Perhaps the most attractive property is that it provides a simple and less...

While fertility is positively correlated across generations, the causal effect of children's experience with larger sibships on their own fertility in adulthood is poorly understood. Using the sex composition of the two first-born children as an instrumental variable, we estimate the effect of...

I study the effects of the level of disability benefits on disability uptake. Estimation of such effects is difficult because individual levels of disability pension benefits are closely related to individual characteristics that may also affect disability uptake through other mechanisms. I...

General Method of Moments (GMM) estimation of a linear one-equation model using panel data with errors-in-variables is considered. To eliminate fixed individual heterogeneity, the equation is differenced across one or more than one periods and estimated by means of instrumental variables. With...

Many empirical studies specify outcomes as a linear function of endogenous regressors when conducting instrumental variable (IV) estimation. We show that commonly used tests for treatment effects, selection bias, and treatment effect heterogeneity are biased if the true relationship is...