Estimating the demand functions for fresh citrus
研究了影响美国新鲜葡萄柚国内及出口需求的因素，使用普通最小二乘法和Zellner两阶段估计法估计四个市场的需求函数，发现Zellner方法得到更显著的系数估计。
Summary The objective of this study was to identify and measure the effects of the factors which affect both domestic (U.S.) and export demand for fresh U.S. grapefruit. The markets included in this study were the U.S., Canada, Japan, and the EEC. To estimate the demand function for fresh U.S. grapefruit in each of the markets, two methods of estimation were used. First, the demand functions were estimated independently by means of ordinary least squares. Secondly, since the demand functions in the four markets may be seemingly unrelated, Zellner's two-stage Aitken estimating prodedure was also used to estimate the demand functions. The results indicated that more significant coefficient estimates for the U.S., Canada, and Japan were obtained using Zellner's procedure.