本研究主要是探討當網際網路的使用存在著消費與生產的外部性時，對電子商務課徵銷售稅的效率影響與福利效果。採用部分均衡分析法，以具有網路外部性的雙占與獨占二種市場模型為基礎，探討產品分別在電子通路與傳統通路銷售時，消費者與廠商的決策、市場均衡，以及最適銷售稅的訂定。本文發現，只要政府有稅收的考量，無論是傳統市場的交易或電子商務都應課徵銷售稅；重要結論如下：(1)若政府為追求社會福利最大，則不應課徵銷售稅；(2)若政府是基於稅收之目的或是在特定稅收下追求社會福利最大，則應對網路外部性較大的電子通路訂定較低的稅率。在銷售稅對效率與分配的影響方面，無論課稅目標為何，銷售稅的課徵都將使得產量減少，市場價格降低。同時，廠商的利潤與消費者剩餘均減少，從而社會福利降低。此外，若電子商務的投入成本與成本節省的差額夠小，則在雙占市場中，原本存在於傳統通路的廠商最終將選擇加入電子商務；而獨占廠商為追求利潤最大，也會提供一個單一的電子通路給消費者。

This research investigates the influence of taxation of electronic commerce on efficiency and welfare, especially the indirect taxation under a sales tax of purchases via the Internet which is characterized by the existence of network externalities. We adopt partial equilibrium approach, based respectively on duopoly and monopoly models with network externalities, which affect both demand and supply, to derive demand function(s), the optimal strategies of firm(s), market equilibrium(s) and the stipulation of optimal sales tax, when products may sell on electronic channel and traditional channel at the same time. We find that, as long as the government takes tax revenue into account, sales tax should be imposed, irrespectively of purchasing channels. The important conclusions are: (1) to pursue the social welfare maximum, the government should not impose sales tax on either local or remote purchases of final goods and services; and (2) to raise maximal tax revenue or to maximize social welfare under the restriction of tax revenue, commodities purchased through Internet should be taxed at lower sales tax rate to reduce harmful effects on network externalities. On the impact on the efficiency of allocation, regardless of the goal of levying taxes, sales tax will reduce output and price simultaneously so that the profits of firm(s) and consumer’s surplus both decline, and thus the social welfare is worsened. In addition, if the difference between the investment cost and the saving of overhead expenses and production cost caused by engaging in e-commerce is small enough, then in the duopoly market, the firm which exists originally in the traditional channel will choose to join e-commerce finally; the monopolist will offer a single electronic channel to consumers in order to pursue profits maximum.

目錄

第一章	緒論
第一節	研究動機與目的……………………………………………………………1
第二節	研究方法……………………………………………………………………3
第三節	論文架構……………………………………………………………………4

第二章	文獻回顧
第一節	電子商務……………………………………………………………………5
第二節	電子商務的租稅分析…………………………………………………..…11

第三章	理論模型
第一節	雙占模型的基本設定……………………………………………..………18
第二節	雙占市場的消費者決策………………………………………………..…19
第三節	雙占廠商的決策與最適銷售稅稅率的決定…………………………..…21
第四節	獨占市場………………………………………………………………..…35

第四章	結論
………………………………………………………………………………..………44
參考文獻
………………………………………………………………………………..………47






表目錄

表1. 雙占廠商之比較基準模型—未導入銷售稅…………………….……...……34
表2. 雙占廠商分別在不同通路銷售之課稅效果……………………….…...……34
表3. 雙占廠商同時在電子通路銷售之課稅效果…………………………..…..…35
表4. 獨占廠商之課稅效果………………………………………………….…...…43

一、中文文獻
1.	王正、徐偉初，1991，財政學，國立空中大學。
2.	王正文，2000，電子商務對銷售稅基的衝突-以美國加州為例，逢甲大學會計與財稅研究所碩士論文。
3.	吳顯東、張文鐘，1998，網際網路的誕生，科學月刊，6期，450-455頁。
4.	邱垂昌，2000，電子商務之課稅與其經濟涵義之探討，中國稅務旬刊，第一七五三期。
5.	林如雪，2001，電子商務之經濟效果初探，台灣大學經濟學研究所碩士論文。
6.	邱祥榮，2002，電子商務課徵加值型營業稅之探析，台灣大學法律學研究所碩士論文。
7.	梁定澎，2000，電子商務理論與實務，華泰。
8.	陳勇勝，2003，電子商務交易對營利事業所得稅及營業稅課稅影響之研究，淡江大學國際貿易學系碩士論文。
9.	楊軍偉、回文博，2001，電子商務的特性與人才培養，e-works http://www.e-works.net.cn。

二、外文文獻
1.	Bruce, D., Fox, W. and Murray, M., 2003, “To Tax or Not To Tax? The Case of Electronic Commerce”, Contemporary Economic Policy, Vol. 21, No. 1, 25-40.
2.	Economides, N., 1996, “The Economics of Networks”, International Journal of Industrial Organization 14, 673-699.
3.	Katz, M.L. and C. Shapiro, 1985, “Network Externalities, Competition, and Compatibility”, American Economic Review, Vol.75, No. 3, 424-440.
4.	Kalakota, R. and Whinston, A., 1997, "Electronic Commerce: A Manager's Guide", Addison-Wesley Professional.
5.	Palma, A. and L. Leruth, 1995, “Variable Willingness to Pay for Network Externalities with Strategic Standardization Decisions”, European Journal of Political Economy, Vol. 12, 235-251.
6.	Zodrow, G. R., 2003, “Network Externalities and Indirect Tax Preferences for Electronic Commerce”, International Tax and Public Finance, 10, 79-97.