糧價穩定、糧食安全與制度設計

Commodity Price Stability, Food Security and Incentive Mechanism

農業為立國之根本，亦是人類文明發展與社會進步之基礎，是以，如何維持糧食數量充裕，以確保糧食安全，至為重要。此外，穀賤傷農、穀貴傷民，糧食價格受制生物性與天候等因素之影響，往往動輒得咎波動劇烈，因此，如何穩定糧食價格，向來是農政單位的首要目標。換言之，農業政策執行的兩大標的：一為維持糧食價格穩定，二是確保糧食安全存量，兩者之間如何取得平衡，實考驗著執政者之施政藝術；此一議題，與總體經濟領域「時序不一致理論」所涉－－兼顧維持充分就業產出與抑制通膨，有著異曲同工之妙，本文第一個目的即在於利用時序不一致理論，探討糧食安全與糧價穩定之問題。本文欲以時序不一致理論為據，嘗試建立一個兼顧糧食價格穩定及糧食安全存量的農政單位所面臨的最適化問題，據以說明「法則」與「權衡」之施政準則如何左右糧價、糧食存量以及民眾福利水準。其次，倘若政府意欲平抑過高的糧價，是否可透過制度設計，將官員所獲薪資與其施政績效聯動，在此情況下官員所從事之決策是否能有效降低糧價及其對社會福利之影響為何，為本文第二個目的。依據本文之分析發現：政府例行性收購比例、調節性收購係數、政策偏好相對權數、存量撥出率等因素是左右社會福利、政府決策、以及糧價與存量高低的關鍵，亦對引入制度設計之成效，具舉足輕重的影響。

The agricultural sector is the foundation of civilization during theperiod of economic development. To stabilize commodity prices andmaintain sufficient food production are two important goals for thegovernment. Most literature discusses these two issues separatelybecause of the conflict nature between price stability and food security,even though they should be considered simultaneously. This situation inwhich the government tries to maximize social welfare throughimplementation of policies under the consideration of two conflict goals isquite similar to the time inconsistency theory dealing with inflation andgrowth in Macroeconomics. In this article, we apply the methodology oftime inconsistency theory to discuss how the Rule and Discretion toaffect the optimal choices of commodity prices and food stocks. Then wewill discuss how the incentive mechanism claimed by Walsh to influencecommodity price and social welfare. The result shows parameters suchas the ratio of government purchase for commodity, the relative weightbetween prices and stocks, and the ratio of government food expenditureare key factors to affect the optimal level of commodity prices, foodstocks, social welfare and the effect of incentive mechanism on theeconomy.