開放進口對臺灣肉類需求體系結構性變動之影響

Abstract

根據農業統計年報顯示，就國人於過去40年間肉類的消費情況而言，其每人每年的消費量快速成長，而豬肉與水產品消費量長期平均佔肉類總消費80%，且各種肉品消費形態也呈現巨幅的改變。過去學者的研究發現，肉品間消費量的交互消長狀況變動，主要的原因可能為過肉品相對價格的改變以及個人所得的成長等經濟因素，而其他如產品因素(食品營養與健康資訊增加、廣告促銷與新產品出現等)、社會經濟因素(人口分配比例、家庭組成、都市化、國際化與經貿自由化等)與飲食習慣因素等，都可能會間接影響國人對於肉類需求形態變遷。 世界貿易組織(WTO)中農業談判部份，最早由1986年關稅暨貿易總協定(GATT)的烏拉圭回合談判開啟，且臺灣於2002年正式加入成為會員。會中決議之農業協定(AOA)更迫使各國進行多方的農業談判，而入會協議的市場開放部分必須取消進口管制與限制進口部份，其他非關稅障礙成份亦需轉以關稅來衡量，並且逐步降低農產品關稅稅率，進而加速開放進口的程度以及整體進口量的提升。在國人飲食習慣與國外顯著不同的情況下，開放外國廉價肉品之大量進口，可能會對國內農產市場造成相當大的衝擊，進而造成需求結構的變遷。 本文的目的在於分析各肉品進口量的改變，對於消費者對各肉品偏好轉變的影響，以及對於肉品價格與個人所得變動的反應，並找尋各肉品可能的需求結構變動時點。究實證模型部分，採用一階差分的近似理想化需求體系，並利用各肉品進口量作為需求結構變動影響因素，來架構臺灣肉類的實證需求體系模型，使用1966年至2005年相關之臺灣肉品需求資料，推估臺灣豬肉、牛肉、雞肉、水產品與其他肉品等五項肉品需求體系各參數。嘗試透過不同的模型設定與估計方法來進行估計，衡量結構性變動偏向型態與發生時點；最後，估算並分析Marshall需求彈性、Allen偏替代彈性與各肉品進口彈性，以及結構變動前後各彈性值的變動狀況。 根據本研究結果發現，開放進口所影響的結構性變動主要來自價格參數，而非支出參數或截矩項的影響，所以各肉品進口量影響因素於模型的設定上，僅需考慮其透過價格參數對於需求結構變動的影響。需求函數價格內生化檢定中，發現臺灣肉類價格會內生影響於需求體系，也就是肉類供給確實存在落遲的現象，使得供給面的變化會影響肉類的需求面，所以須以反覆三階段最小平方法(I3SLS)法來進行實證估計。結構性變動偏向的衡量上，發現各肉品進口量所影響的結構性變動型態，在1966年至1978年間明顯的主要偏向於增加牛肉與水產品消費，於1979年至1988年間轉為主要偏向牛肉，於1988年至2000年轉為主要偏向牛肉與其他肉品，而2001年至2005年轉為主要偏向牛肉、雞肉與其他肉品；其中牛肉可能在1975年間發生需求結構變動，而豬肉、雞肉、水產品與其他肉品的部份可能在1999間年發生。 根據本研究所估得的各彈性結果，發現在開放進口的影響下，除了少數幾項產品的毛(淨)替代(互補)關係較大外，大多數兩種肉品之間的關係並不強。進口彈性上，以牛肉的彈性值最大，顯示牛肉受進口量的影響最大。由結構變動偏向型態來看，各肉品可能發生結構變動的時間點不盡相同，而由變動前後消費者反應的變化中可發現，消費者對於豬肉、雞肉與其他肉品之需求趨勢與價格變動的反應皆轉變為較敏感，也就是容易受到價格與支出變動而影響需求量改變，而牛肉與水產品部分則轉為較不敏感。對進口量變動的反應上，以牛肉彈性的增加幅度最大，而豬肉與其他肉品也有些微的上升，其中雞肉指標彈性部分更由負值轉為正值，顯示結構變動後進口量的變化上，會影響雞肉支出份額轉為顯著的上升。

The Purpose of this master thesis was to provide an empirical method to analyze the structural change effect of meat consumers by Imports in Taiwan. Analyze the change of Import quantity further, whether the reaction influenced consumer to change for the hobby of the each meat, and change to meat price and personal income of reaction. And then search the possible structure change point of each meat. Understand the condition of meats demand characteristic and its structure change, can provide domestic manufacturer and government parties concerned, by with establishment future the plan of the industry adjust and development, or draft manufacturer and consumer to protect the reference of measure. This study take the import quantity (thousand ton) as the impact factor, and the gradually switching almost ideal demand system (AIDS) model was employed to estimate the meats demand system in Taiwan during 1966-2005. Under the assumption of products weakly separability, the meats in this study were categorized into pork, beef, chicken, fish and other meats. Try through the different model set and estimate method to estimate demand system, and measure both the partial type of structure change and take place points. Finally, 1)Estimate and analyze Marshalliam demand elasticities, Allen partial elasticities of substitution and the elasticities of import; 2)Analyze the change condition of each elasticities of structure change in front and back. The results of Log-likelihood ratio test indicates that the structural change effect of import quantity is mainly derived from the parameter of price, and Wu-Hausman test also reveals that prices for meats are endogenous in demand system. So the meats demand system in this empirical research, need to set price as the structural change source and make use of the I3SLS method to carry on. And then the transition period of structural change shows that the beef took place in 1975 in Taiwan, and others appeared in 1999 simultaneously. Based on the estimated demand elasticities, under the influence of Imports, in addition to few gross (net) substitutes and complements, the subtitutability and complementarity between most of the two meat product are small. Accroding to elasticities of import, the elasticity of beef is the biggest, showing that beef is the meat product that take the influence of Imports most. The variety changed in front and back consumer reaction points out, consumers become more sensitive to reaction of pork, chicken and other meats demand or price, is easily changed by price and expenditure and caused demand change. However, beef and fish products then turn into less not sensitive. The reaction of import quantity change could find that the increment range of beef elasticities is the biggest, pork and other meats also have some tiny raise. Furthermore, chicken even turns the value by negative into positive, and the increase of import quantity of chicken will improve its expenditure share after structural change.