Conventional studies of bilateral trade patterns specify a log-normal gravity equation for empirical estimation. However, the log-normal gravity equation suffers from three problems: the bias created by the logarithmic transformation, the failure of the homoscedasticity assumption, and the way zero values are treated. These problems normally result in biased and inefficient estimates. Recently, the Poisson specification of the trade gravity model has received attention as an alternative to the log-normality assumption (Santos Silva and Tenreyro, 2006). However, the standard Poisson model is vulnerable for problems of overdispersion and excess zero flows. To overcome these problems, this paper considers modified Poisson fixed-effects estimations (negative binomial, zero-inflated). Extending the empirical model put forward by Santos Silva and Tenreyro (2006), we show how these techniques may provide viable alternatives to both the log-normal and standard Poisson specification of the gravity model of trade.

Additional Metadata
Keywords distance, gravity model, international trade, modified Poisson models
JEL C82, Methodology for Collecting, Estimating, and Organizing Macroeconomic Data (jel), F17, Trade Forecasting and Simulation (jel), M, Business Administration and Business Economics; Marketing; Accounting (jel), M13, New Firms; Startups (jel), O32, Management of Technological Innovation and R&D (jel)
Publisher Erasmus Research Institute of Management (ERIM)
Persistent URL
Burger, M.J, van Oort, F.G, & Linders, G.J.M. (2009). On the Specification of the Gravity Model of Trade: Zeros, Excess Zeros and Zero-Inflated Estimation (No. ERS-2009-003-ORG). ERIM report series research in management Erasmus Research Institute of Management. Erasmus Research Institute of Management (ERIM). Retrieved from