不同排放交易市場結構下之先期減量獎勵政策研究

Credit for Early Action Policies in Emissions Trading Systems under Different Market Structures

林欣怡(Hsin-Yi Lin)

指導教授 ： 李叢禎

國立臺北大學/社會科學學院/經濟學系/碩士(2008年)

摘要

京都議定書生效後，非附件B國家對於負擔後京都時期減量責任之預期驟升，是否應透過獎勵政策提供誘因，促使廠商及早採取減量行動，儼然成為近年來實際政策設計與學術研究中重要議題。先期減量獎勵政策(Credit for Early Action, CEA)，特指政府依據廠商先行期的減量水準，作為核配排放權依據，以獎勵廠商進行減量的政策。本文內容著重於探討不同排放交易市場結構之CEA政策的最適設計，以及CEA政策對於排放交易市場之均衡結果與效率的影響。
本研究結果顯示，在給定相同的國家減量目標下，排放交易市場結構並不會影響CEA政策的制定，不論排放交易市場為完全競爭或不完全競爭，政府針對廠商每單位先期減量所核配之排放權應相同，但排放交易之均衡結果與效率則取決於交易市場結構。進一步比較兩排放交易市場的均衡結果，我們發現，排放權價格的差異取決於所有價格接受廠商所能取得之排放權數量。若所有價格接受廠商所能取得之排放權數量較少，則在該排放交易市場結構下的排放權均衡價格將較高，反之則反是。另一方面，因為排放權價格對價格接受廠商各期邊際減量效益的影響都為正，對優勢廠商的影響則為不確定，又，由於不論排放交易市場的結構為何，邊際減量效益的高低，將影響廠商的減量決策，且在CEA政策之下，一旦廠商選定各期的減量水準，則其於遵行期受核配的排放權數量與交易數量都將被決定，故當排放交易市場由完全競爭轉變成不完全競爭時，價格接受廠商的減量水準、受核配的排放權數量以及交易數量的變動都將取決於排放權均衡價格的相對高低，但對於優勢廠商而言，相關變動則無法由排放權均衡價格的相對高低判斷。當市場結構轉變時，若排放權均衡價格增加，則價格接受廠商各期邊際減量效益增加，廠商將同時增加各期的減量水準，其受核配的排放權數量因而增加，如此，排放權買方之交易數量將減少，而排放權賣方之交易數量則將增加。
最後，本研究比較CEA政策與溯往原則兩種排放權核配方式下，排放權交易之均衡結果，並說明不同核配方式對於排放交易效率的影響。分析結果顯示，當排放交易市場結構為完全競爭時，不論排放權的核配方式為何，政府均可以最低的遵行成本，達成既定的國家減量目標。然而，當排放交易市場結構為不完全競爭時，若優勢廠商受核配的排放權數量與其實際排放量不同，則該廠商將有誘因影響排放權價格，效率損失因而產生。當兩種核配方式都會產生效率損失時，排放交易市場的相對效率性，將視在不同核配方式下，廠商的減量決策而定，故我們無法判別此時CEA政策是否能有效降低國家的遵行成本。

關鍵字

先期減量獎勵政策 ； 排放交易市場結構 ； 先期減量 ； 排放交易 ； 排放權核配

並列摘要

After Kyoto Protocol is formally in effect, the non-Annex B countries’ concern about being subsumed in post-Kyoto Protocol has rising. For this reason, whether to encourage firms to initiate their abatement actions earlier has becoming an important issue in environmental policy design and relevant academic research. Credit for early action (CEA) is a policy which aims at early emissions reduction. Under such a policy, the government would allocate emission allowances based on firms’ abatement levels prior to the compliance period. The purpose of this thesis is to analyze the optimal designs of CEA policies in emissions trading systems under different market structures. The effects of CEA policy on equilibria and efficiency of the emissions trading system are also explored.
It is shown that the optimal design of CEA policy would not be influenced by the market structure of emissions trading system given a particular national emission cap. The amounts of emissions allowances allocated to firms for their early carbon abatements are the same under perfect and imperfect competitive emissions trading systems. However, the equilibrium trading outcomes and the efficiency may still be different under the two systems with the same CEA policy. The relative magnitudes of the equilibrium allowance price hinge on the numbers of emission allowances available to the price-taking firms. The fewer the numbers of emission allowances available to the price-taking firms, the higher the equilibrium allowance price will be and vice versa. Then, it is the allowance price that determines the relative magnitudes of the price-taking firms’ optimal abatement levels, the amounts of emission allowances that they receive from the government and those that they exchange in the market when the trading system changes from perfect competitive into imperfect competitive. Yet, the corresponding variations for the dominant firms cannot be told by the difference of the allowance price. Precisely, if the equilibrium allowance price increases as the trading system changes from perfect competitive into imperfect competitive, the price-taking firms’ marginal benefits of abatement in each period increase. Therefore, their optimal abatement levels in both periods and the amount of emission allowances that they receive from the government increase. For price-taking firms that are buyers of emissions allowances, the amount of emission allowances that they exchange in the market would decrease. Contrarily, for price-taking firms that are sellers of emissions allowances, the amount that they exchange would increase.
Finally, we compare the equilibria of emissions trading system under the CEA policy and the grandfathering rule to analyze the influence of the rule of emission allowances allocation on the efficiency of the trading system. It is found that the total compliance costs for meeting the national carbon emission cap are minimized no matter what rule of emission allowances allocation is in the perfect competitive trading system. In the imperfect competitive trading system, the dominant firms would have incentive to manipulate the allowance price once the amounts of emission allowances allocated to them are different from those that they demand in equilibrium, and hence the efficiency loss occur, on the other hand. If there is efficiency loss when either of the rules of emission allowances allocation is undertaken, the relative efficiency would depend on firms’ carbon abatement decisions under different rules. Thus, it is uncertain whether adopting the CEA policy is more efficient for the government to meet the national carbon emission cap in this case.

並列關鍵字

Credit for Early Action ； market structure of emissions trading system ； Early Action ； Emissions Trading ； emission allowances allocation

參考文獻

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