不完全競爭市場從價與從量稅之比較---考慮租稅逃漏的情況

Abstract

傳統探討從價與從量兩種稅制之比較的文獻都忽略租稅逃漏的事實，因而本計畫擬在存在租稅逃漏的經濟體系之下進行此二種稅制福利效果之比較。由於從價與從量兩種稅制給予廠商進行租稅逃漏的誘因並不相同，因此造成此二種稅制即使在完全競爭市場下亦具有不同的福利效果。實務上在銷售稅的逃漏當中，廠商可以採取低報數量或是低報價格進行租稅逃漏，值得注意的是，不管低報數量抑或是低報價格都需要作帳成本。在這樣的背景下，當稅制為從量稅制時，並沒有低報價格的誘因，因而廠商只會採取低報數量來進行租稅逃漏；然而當稅制為從價稅制時，廠商則同時有低報數量與價格的誘因，此一結果造成此二種租稅工具福利效果的不同。此外，鑑於大部分文獻都是在不完全競爭市場的架構下進行此二種稅制福利效果之比較，因此本研究計畫將延續傳統文獻探討寡占的市場結構下探討從價與從量兩種稅制之比較，所獲致的結果將與傳統文獻作一比較。計畫中將探討Cournot-Nash 的數量競爭模型以及Betrand 的價格競爭兩種情況。

Evasion on commodity taxes is important. Slemrod (2007) cites a confidential study made in 2005 by the Forum on Tax Administration (a subsidiary body of the OECD’s Committee on Fiscal Affairs). Estimated noncompliance rates for value-added tax range from 4.0 to 17.5 percent for some countries in the study. Silvani and Brondolo (1993) investigate noncompliance of value-added tax for 19 mostly developing countries. Comparing the actual value-added tax revenue with the potential tax base, they find a median evasion rate of 31.5 percent, with New Zealand the lowest at 5.1 percent while Peru the highest at 68.2 percent. However, the literature on the efficiency of indirect taxes under imperfect competition neglects the tax evasion problem. In this project, ad valorem and unit taxes will be compared under imperfect competition with tax evasion. It firstly finds out that: once there is evasion, evading specific taxes must be via underreporting quantities sold, whereas evading ad valorem taxes can be via underreporting selling prices as well as quantities sold. As a result of more instruments available to evade taxes, a firm can implement evasion with a lower resource cost under ad valorem than specific taxation. This is the reason why the two tax types make a different welfare effect. It is worth noting that both Cournot quantitative competition and Bertrand price competition will be studied in the project