目標區政策對農產品價格穩定性之研究

The Study of Agricultural Price Stabilization in a Target Zone Policy

本文嘗試將國際金融之目標區政策應用於農產品價格管制的議題。我們將延伸Frankel（1986）及Lai、Hu 與Wang（1996）分析農產品市場的概念，配合目標區政策及聯立隨機微分方程之方法，來探討當農產品及非農產品價格皆可瞬時調整時；若政府宣告目標區政策，民眾的預期將如何影響農產品價格及其他經濟變數之穩定性。明確地說，我們想根據此模型來分析：當政府宣告實施目標區政策時，對農產品價格是否亦會產生如Krugman（1991）所說的「蜜月效果」；同時也探討此項干預政策對其他非農產品價格，是否可能需要付出波動更加劇烈的代價。從數值模擬分析，本文所得之結論為：首先，當政府宣告目標區政策時，若民眾亦相信政府會確實實行此項政策；透過預期的改變，對於農產品及非農產品價格的影響，其間和農產品與債券間替代程度的大小有密切關係。一般而言，替代程度的越小，農產品及非農產品價格波動亦變小，即有蜜月效果存在；反之則否。其次，將目標區的範圍縮小後，並不一定會使農產品及非農產品價格的波動穩定，亦和此替代程度的大小有密切關係。此和Krugman（1991）、Klein（1990）不同的結果或許可作為政府實行目標區政策之參考。

This paper tries to analyze the agricultural price control issue fromthe view point of target zones. We extend Frankel (1986) and Lai、Huand Wang (1996) models, where using target zone policy andsimultaneous stochastic differential equation methods, to investigatewhether the honeymoon effect proposed by Krugman (1991) is presentwhen the government adopts a target zone policy on agricultural prices.Preciously, we want to know how authorities’ commitment to defendingan agricultural price target zone will affect the public’s agricultural priceexpectation, and in turn reduce actual agricultural price.With the plausible parameter values, the conclusion of this paper isas follows. Firstly, the public’s expectation will affect the economicstability when the government announced a target zone policy, and thiseffect is relates to the degree of asset substitutability between agriculturalproducts and bonds. In general, the volatility of agricultural and nonagriculturalproduct prices will reduce if this asset substitutability degreeis small; the reverse is true. Secondly, the more narrow target zonebands does not smaller the volatility of agricultural and non-agriculturalproduct prices, and it’s closed relate with the degree of assetsubstitutability between agricultural products and bonds as well.