Firm-level innovation is investigated using three probit panel estimators, which control for unobserved heterogeneity, and a standard probit estimator. Results indicate the standard probit model is misspecified and that inter-firm networks are important for innovation.

Wansbeek and Bekker considered a new estimator for simple dynamic panel data models (where there are no exogenous variables) which involved a complex weighting matrix. An operational variant of this estimator is proposed which is applicable to the more realistic case where there are exogenous...