本文主要探討當中間財（能源或是原物料）的價格變化，是否促 使廠商投入更多的節能研發以其對社會福利的影響。本文設立了一個 兩階段賽局分析的理論模型，在上游中間財為完全競爭市場，下游有 兩家最終財廠商為雙占市場的設定下，第一階段是下游廠商的節能研 發決策，第二階段則是同質雙占下廠商的Cournot 競爭。 本文發現，廠商使用中間財的價格提高有可能使得節能研發投入 增加或減少，端視中間財的價格高低而定。當廠商面對很高的能源或 中間財價格時，此一價格的提高反而會使下游廠商減少節能研發。再 者，在既定的中間財價格下，僅單一廠商節能研發的最適研發投入， 是有可能會比兩家廠商投入節能研發的社會福利較高或低，端視中間 財的價格與邊際成本增加速度大小而定。當節能研發投入的邊際成本 遞增速度不大時，兩家廠商投入節能研發反而會帶來較小的社會福利， 代表了兩家廠商同時投入做研發，有可能會出現過度投資的問題，反 而使得社會福利水準降低。;This dissertation mainly discusses whether the price change of intermediate goods (energy or raw materials) will prompt manufacturers to invest into input-saving R&D and its effect on social welfare. Assuming that the upstream intermediate goods market is perfect competitive and there exist two downstream manufacturers who engage in Cournot competition and possible input-saving R&D. This dissertation builds a theoretical model of two-stage game. The first stage is the input-saving R&D decisions of the downstream manufacturers, and the second stage is the Cournot competition of the homogeneous firms. This dissertation finds that the increase in the price of the intermediate goods may increase or decrease the investment in input-saving R&D, depending on the level of intermediate goods price. When the price of intermediate goods is high enough, an increase in the price may counterintuitively reduce the input-saving R&D. As for the welfare, the case only one manufacturer invests in R&D may yield a higher welfare level than that both firms invest in R&D as long as the increasing rate of the marginal cost of the R&D is not so large. This finding is also interesting and counterintuitive. However, the case neither firm invests in R&D brings the lowest social welfare level.
