Testing the Alchian–Allen theorem for three goods using the pseudo Poisson model
检验了阿尔钦-艾伦定理在三种商品世界中的成立性，通过分析全球咖啡贸易数据，发现共同单位运费提高了咖啡的整体质量需求，并采用伪泊松极大似然法克服了样本选择偏差和异方差问题。
Abstract We show that the Alchian–Allen theorem holds in three‐good world. We empirically test the theorem by examining the relative demand for three quality‐differentiated coffee varieties sold globally and confirm that a common per‐unit charge increases the overall quality of coffee demanded. Our empirical specification employs the Poisson pseudo maximum likelihood method, which prevents sample selection bias when zero flows between country pairs occur and estimated parameter inconsistency when the data exhibit heteroscedasticity. This is a significant improvement compared to previous practice of using the ordinary least squares to estimate the log‐log formulation, which led to both biased and inconsistent parameter estimates.