不同市場結構下排放權交易機制分析

Emission Trading and Market Structure

工業生產所排放的溫室氣體與全球氣候變遷有密切的關聯性，因此，溫室氣體排放量的抑制成為世界各國急需解決的重要議題。排放權交易（emission trading）為1997年京都議定書所建議的一項政策。雖然Hahn（1984）與Westskog（1996）以靜態與不完全競爭市場為分析基礎，但以往對於該項政策的研究多以靜態與完全競爭市場分析為主（Baumol and Oates,1971；Montgomery, 1972）。Rubin（1996）、Kling and Rubin（1997）則探討跨期排放權交易政策的可行性與其影響，不過仍然建立在完全競爭的排放權市場結構上。本研究則於動態體系下分析不同市場結構（即完全競爭與不完全競爭）的排放權交易機制。本研究發現若商品市場、傳統要素市場與排放權交易市場均為完全競爭結構，則所有廠商的邊際防治成本都相同，且其跨期的排放權交易市場具有成本效率性；則在穩定狀態均衡下，若所有廠商的總排放權稟賦固定，廠商間排放權稟賦分配原則不會影響防治成本效率性。但若具有價格制訂能力的優勢廠商為排放權交易市場的獨賣者，則當經濟體系站穩定狀態均衡時，優勢廠商的排放權需求價格彈性為-1，故改變優勢廠商的排放權稟賦會影響個別廠商的防治成本與所有廠商的總防治成本。可知主管單位可以透過降低優勢廠商的排放權稟賦，而降低所有廠商的總防治成本。

The emission of greenhouse gases has significant impacts on the global climate change. The issue of CO2 reduction has become an important role for most countries in the world. Emission trading is one of important policies proposed in 1997 Kyoto Protocol. Even Hahn (1984) and Westskog (1996) concluded that the emission trading market was static but imperfect competition, most previous studies assumed that the market of emission trading was static and perfect competition (Baumol & Oates, 1971; Montgomery, 1972). Rubin (1996) and Rubin & Kling (1997) began to treat the market of emission trading was dynamic and perfect competition. This study employs the theory of dynamic optimization to analyze the mechanism of emission trading under the perfect competition and oligopoly respectively. This study concludes that the marginal CO2 abatement cost for each firm is equal when all of three markets, general commodity, traditional factor and emission trading, are perfect competition. And the equilibrium solution of the intertemporal emission market is cost effectiveness. Besides, in the steady state, if the total emission endowment is constant, the rule of distribution of emission endowment among the competitive firms will not affect the cost effectiveness. However, for the monopoly, the dominant firm decides the price of emission permit. The demand elasticity of emission permits is -1 in the steady state. Thus, the cut-down of initial emission endowment of the dominant firm will affect each firm's abatement cost and reduce the total abatement costs for all firms.