臺灣養殖魚類需求體系之研究－－逆需求體系模型之應用

A Study of the Inverse Demand System of the Aquaculture Products in Taiwan

本研究以國內主要的養殖魚類產品（吳郭魚、目魚、及其它養殖魚類產品）為研究對象，就其供給是相當地缺乏彈性的特性，應用五類逆需求體系模型進行實證分析並選擇出最適模型組合逆需求體系，以建立國內養殖魚類產品之需求體系，並應用完全資訊最大概似估計方法進行參數之估計並求算出規模彈性及價格反應彈性。研究結果顯示，虱目魚、吳郭魚及其他魚種的價格反應估計值分別為-0.664、-0.367 -0.015，顯示了虱目魚的可供消費量對養殖魚類產品的影響較其它兩類魚種來得顯著。又亂目魚的消費量對於吳郭魚和其它魚種的價格之影響分別為-0.302 -0.320。在規模彈性估計值方面，實證結果顯示當增加1%的養殖產品總消費量時，會導致吳郭魚的價格下跌0.96%；虱目魚的價格下跌1.17%；其他魚種的價格下跌0.67%。本研究結果顯示虱目魚在我國養殖魚類產品中扮演重要的角色。

Based on both quantity and value production, aquaculture plays a very important role in Taiwan fishery production. This study used the demand theory to develop a demand system for the aquaculture products in Taiwan. The supply of the aquaculture products is quite inelastic, indicating an inverse demand system with prices dependent on quantities may be more appropriate than the direct demand system. This study examined and compared five inverse demand systems using monthly transaction data from the fish markets in Taiwan area. For the Taiwan's aquaculture products and for the modelling price-dependent demand, a synthetic model is more appropriate than other inverse demand models. Results of this study indicates that milkfish has the highest own-flexibility at -0.664, with tilapia and other aquaculture fishes having own-flexibilities of -0.367 and -0.015, respectively. In addition, a one-percent increase in aggregate quantity of aquaculture fishes would result in decreases in the normalized prices of 1.17%, 0.96% and 0.67% for milkfish, tilapia and other aquaculture fishes, respectively.