臺灣肉類需求的結構變動分析

The Structural Change of Demand for Meat in Taiwan

本研究利用漸進調整（Gradually switching）一階差分AIDS 模型估計臺灣肉類的需求體系。在肉類產品與其他商品具弱可分割性（weakseparability）的假設下，將肉類分成五類，分別為漁產品、雞肉、豬肉、牛肉及其他肉類等。實證結果顯示，台灣肉類消費型態以1983-1987 年期間為結構變化的轉換期。概似比檢定結果顯示，加入結構變數於台灣肉類需求體系的截距項、總支出及價格等估計參數中是較適合的設定模式。Wu-Hausman 檢定顯示台灣肉類價格內生決定於需求體系。另外，結構變化參數對截距項的影響為：漁產品的消費額比例有隨時間增加而遞減的現象，雞肉則有增加的趨勢；另外，結構變化後漁產品的支出彈性變得較具彈性，雞肉變得較不具彈性。漁產品的支出彈性顯著的從結構變化前的0.91 上升為結構變化後的1.65，雞肉則從1.16 下降至0.51。就自身價格彈性而言，漁產品顯著的由結構變化前的0.49 上升為0.96，豬肉則從0.79下降至0.66。

This study used the gradually switching almost ideal demand system(AIDS) model to estimate the meats demand in Taiwan. Under theassumption of products weak separability, meats are categorized into fish,chicken, pork, beef and others meat. The results of this study show thatthe transition period of structural change for meats appears between1983-1987 in Taiwan. Log-likelihood ratio test also indicates that ademand system, which includes structural change variable in intercept,expenditure and price terms, is a more appropriate specification. Inaddition, Wu-Hausman test also reveals that prices for meats areendogenous in demand system. The demand structure for meat displaysthat the demand for fish decreases; however, chicken demand increases.Finally, the expenditure elasticity was 0.91, 1.16 and 1.05 for fish,chicken and pork respectively before structural change. It wassignificantly changed to 1.65, 0.51 and 0.82 after structural change.The own-price elasticity had a significant change from 0.49 and 0.79 to0.96 and 0.66 for fish and pork.