考慮碳稅之存貨管理模式發展與分析

Abstract

碳稅目前為各國政府對抗暖化並實現綠色經濟的重要政策工具之一，此課稅機制為反映使用能源所造成的二氧化碳排放的外部成本內部化，促使排放源進行減量。碳排放許可權則是利用碳交易總量管制之概念所延伸而來，當企業的碳排放量超出許可權所規範的排放量，將對超額部分課稅，有別於碳交易之碳價會隨著市場波動。累進稅制與累退稅制亦為租稅理論重要之機制。因此本論文參考Hua et al., (2011)所發展總量管制與交易制度之經濟訂購批量(Economic Order Quantity, EOQ)模式，推導出碳稅、碳排放許可權、累進稅制與累退稅制之EOQ存貨管理模式，同時探討有效稅率，並利用模擬數據作為模式之前提假設，計算出以上四種稅制總成本、訂購量與碳排放量，並進一步作比較分析。本篇研究發現各個政策之總成本、訂購量與碳排放量，企業之總成本隨著稅率的上升而逐漸增加，而訂購量和碳排放量則反之。此外，碳排放量遞減的幅度主要受到訂購量的影響。其中，累退稅制因受限於前提假設所計算出之碳排放量尚未達到邊際成本遞減效果之規模，才使得其總成本高於其他政策，與預期結果相異。而累進稅制之總成本，相較於碳稅與碳排放許可權之總成本高，且碳排放量最低。 碳交易是在總量管制的限制下，讓企業可透過市場公開交易溫室氣體排放權的方式，以較低成本達到溫室氣體減量之目的。蕭代基等人(2010)透過碳稅與碳交易之意涵與特點分析，認為兩者相互為「競爭性的政策工具」，也就是其優缺點頗為互補。因此本研究亦將碳稅與碳交易於EOQ存貨管理模式之總成本、訂購量和碳排放量進行比較，發現碳稅政策之總成本高於碳交易政策，遞增幅度也最大。最後透過各個制度特點之探討，進一步比較其經濟效率性、價格訊號、環境有效性等面向，作為政府在規劃溫室氣體減量政策時的參考，設計不同政策工具之最適搭配，以真正落實節能減碳的目標，同時減少產業衝擊。企業則可依據各稅制之特性進行財務規劃、採行不同的營運策略，以增進國際競爭力。

Carbon tax is an important tool for governments to combat global warming and achieve green economy. The policy reflects carbon dioxide emissions from the use of energy and internalization of external costs by the taxation mechanism, and prompts the sources of emissions reductions. Allowance of carbon emissions is extended from the concept of carbon cap-and-trade. When carbon emissions are beyond the license regulated by governments, corporations will have to pay extra taxes from excess volumes of carbon emissions. Different from the carbon trading price with which the carbon price rises with the market volatility, progressive tax and regressive tax system are also an important mechanism of tax theory. This paper references the carbon trading EOQ inventory management model developed by the study of Hua et al., (2011), and further derives four EOQ inventory management models, respectively the carbon tax, carbon emissions permissions, progressive taxation and regressive taxation. Not only do we explore effective tax rate, but we also set model assumptions to calculate the total cost, order quantity and carbon emissions the above four tax policies, and further do comparative analysis. Shaw et al. (2010) implied that characteristics of the carbon tax and carbon trading are "competitive policy tools ", that is, their advantages and disadvantages are quite complementary. Therefore, this study also respectively compares the total cost, order quantity, and carbon emissions in the EOQ inventory management model applied to a carbon tax and carbon trading. Finally, through further analysis of economic efficiency, price signals, and environmental effectiveness, our study result can be a reference in the planning of the greenhouse gas reduction policy. Based on the characteristics of each tax system for financial planning, enterprises should adopt different business strategies to enhance their international competitiveness.