台灣地區農業公共投資與農業土地生產力的關係

Interrelationships between Public Investment in Agriculture and Agricultural Land Productivity in Taiwan

本文利用我國農業部門的總體資料，在生產函數中除了考慮原有之勞動與資本投入變數外，更進一步以政府對農業部門公共投資做為非農業部門投入的替代變數，探討我國農業公共投資（公共投資／土地）與農業土地生產力（產出／土地）的互動關係。我們以Akino 與Hayami (1974) 的模型為基礎，針對台灣地區1952-2001 年的資料，在考量變數間內生結構性變化（endogenous structural break）下，檢測農業公共投資與農業土地生產力的長期及短期動態關係。我們的主要發現如下：第一，由共積檢定得出，農業公共投資與農業土地生產力在長期間呈顯著正向關係，農業公共投資的土地生產力彈性為0.555。第二，在控制內生結構性變化下，農業土地生產力模型的長期均衡關係依舊獲得支持。第三，由弱外生檢定結果指出，長期間農業公共投資與土地生產力互為因果關係，顯示長期間農業部門的成長必須立基於政府對農業部門的公共投資；而在農業部門的成長的過程中，將可刺激政府對農業部門的公共投資，兩者相互影響。第四，由短期誤差修正模型檢定發現，農業公共投資是體系內失衡發生時的主要調整力量。第五，短期間農業土地生產力對農業公共投資的單向因果關係成立，反之不成立，由此顯見短期間政府無法彰顯對農業公共投資的成效。

This paper investigates the interrelationship between publicinvestment in agriculture (public investment/land) and agricultural landproductivity (output/land) in Taiwan covering the 1952-2001 period. Ourmain findings are as follows. First, the cointegration test reveals thatpublic investment in agriculture and the productivity of agricultural landboth exhibit a significant positive relationship in the long run, where theelasticity of land productivity in relation to public investment in agricultureis 0.555. Next, when controlling for endogenous structural breaks, thelong-run relationship for the productivity of the agricultural land model isstill supported. Third, the results of the weak exogeneity test indicate thata bi-directional causal relationship exists in the long run between publicinvestment in agriculture and the productivity of land. Fourth, from theshort-run error correction model estimation it is found that publicinvestment in agriculture is a major means of adjusting for thedisequilibria that occur within the system. Finally, in the short run theunidirectional causal relationship in terms of the productivity ofagricultural land on public investment in agriculture is established,otherwise it is not established. From this it can be seen that in the shortrun the government is unable to reveal the effectiveness of its publicinvestment in agriculture.