TESTING FOR AGGREGATION AND SIMULTANEOUS BIAS IN U.S. SOYBEAN EXPORT EQUATIONS

Most previous estimates of elasticities of export demand for U.S. soybeans have emanated from single import equations subject to aggregation and simultaneous equation bias. This analysis tests U.S. soybean export data for aggregation and simultaneous equation bias and divides the aggregated data into six market equations to reduce these biases. Elasticity estimates from the six equations are compared with elasticity estimates from single equation OLS and 2SLS estimations using the same aggregate data. Results suggest that distortions from unjustified 2SLS estimation may exceed those from aggregation bias.