5.2. Potential endogeneity problem: consumer health
information and utilization
The propensity to use physician services is likely to be correlated with the choice to use potential substitutes for health care services.This is why controlling for sample selection is so important. The lambda might alleviate the endogeneity bias if the propensity to use medical services at all, which is what lambda will be picking up, drives both information seeking and the number of visits. However we cannot assume that controlling for sample selection eliminates the concern associated with estimating a causal model of health
information on health demand.