貿易自由化與國內、外畜禽市場價格長期均衡關係之研究

Trade Liberalization and Long-Run Equilibrium Relationships Between Domestic and International Livestock Prices

本文旨在測試貿易自由化對我國與國際畜禽產品市場價格之長期均衡關係，以了解貿易政策對國內外禽畜產品市場運作特色及價格間之相互關係與影響，並提供禽畜業有關問題調整與改善之參考。文中以台灣畜禽產業為研究對象，利用Engle and Granger(1987)所提出的共整合理論(cointegration theory)，採用ADF、PP單根檢定法以及Johansen-Juselius之最大概似估計法檢定共整合關係，探討國內與國際畜禽產品市場長期間之因果關係或共整合情形，而為求實證之正確性，再透過Granger representation theorem對共整合模型加以修正，引入誤差修正觀念，建構誤差修正模型（error correction model，簡稱ECM）作為實證應用模型。實證結果顯示：(1)民國64～85年之國內與國際牛肉價格具有共整合關係，且其間具有反饋效果，亦即民國64～85年之國內與國際牛肉價格具有長期之互動與調整關係。在短期方面，民國64～85年之國際牛肉價格具有領先國內牛肉價格變動之趨勢，但國內牛肉價格並無領先國際牛肉價格變動之趨勢。(2)民國55～63年之國內與國際牛肉價格、民國55～85年之國內與國際豬肉價格以及民國55～85年之國內與國際雞肉價格，均不具有共整合關係。綜合而言，已開放自由貿易時期的國內牛肉市場與國際牛肉市場存在長期均衡的共整合關係，亦即彼此價格呈現國際共移型態(international comovement pattern)，而牛肉尚未開放自由進口時期及具進口貿易障礙的豬肉及雞肉市場之國內、外價格均不具長期均衡關係，此顯示貿易障礙的解除與禽畜產品市場共整合有正面的關聯，也隱喻貿易自由化對國內外畜禽產品市場整合具有正面影響，價格間的因果關係有較確定的方向而促進空間的均衡，並使市場機能發揮。

The main objective of this study was to explore the relevance of trade liberalization and the market integration conditions between domestic and international livestock markets. By applying the theory of cointegration, we adopted Unit Roots Test and Cointegration Method to analyze the long-run cointegrating relationships between the livestock markets of Taiwan and the world. In order to increase the reliability of the empirical results, error-correction model (ECM) was adopted as the cointegration method. The empirical analyses revealed that although all of the livestock markets showed short-run relationships between the domestic and the international markets, and the international prices led the domestic prices, the long-run cointegrating relationship existed only between the domestic and the international beef markets. Since the beef market is the only livestock market exists no non-tariff trade barriers in Taiwan, the results imply that trade liberalization could help improving the long-run cointegrating relationship between domestic and international livestock markets. Also, it has positive influences upon the status of international market integration.