Heterogeneous effects are prevalent in many economic settings. As the functional form between outcomes and regressors is generally unknown a priori, a… [read more]

Nonlinear price schedules generally have heterogeneous effects on health-care demand. We develop and apply a finite mixture bivariate probit model to… [read more]

In the presence of heteroscedasticity, conventional standard errors (which assume homoscedasticity) can be biased up or down. The most common form of… [read more]

Instrumental variable estimates of causal effects can be biased when using many instruments that are only weakly associated with the exposure. We… [read more]

Hurdle models are frequently used to model count data. Recent developments in the count data literature make it possible to relax commonly imposed… [read more]

When health insurance reforms involve non-linear price schedules tied to payment periods (for example, fees levied by quarter or year), the empirical… [read more]

In a recent article Newey and Windmeijer (Generalized method of moments with many weak moment conditions. Econometrica 2009; 77(3): 687-719) propose a… [read more]

Hurdle models based on the zero-truncated Poisson-lognormal distribution are rarely used in applied work, although they incorporate some advantages… [read more]