有效保護率與外人直接投資

Effective Rates of Protection and Foreign Direct Investment

有效保護率(effective rate of protection, ERP)為衡量一國貿易保護程度的重要指標，其概念為Corden於1966年首先提出。Corden假設市場為完全競爭，利用附加價值之概念分析一國關稅結構對國內廠商之保護程度。文獻上對此一指標之討論相當廣泛，主要為考慮當模型存在要素替代性、非貿易財、匯率、不完全競爭市場及跨國企業時，Corden之指標該如何修正。近年來，由於資本的全球化與自由化，外人直接投資(foreign direct investment, FDI)已多如過江之鯽。然而，實務上在計算有效保護率時往往忽略了此一經濟行為對有效保護率之影響。本研究之主要目的為透過Anderson(1998)對有效保護率的定義，探討當市場為寡占時，FDI對ERP的影響。本文發現當考慮國外廠商可能進行FDI時，一國之有效保護程度未必會隨其對最終財之進口關税增加而上升。此一發現與傳統探討ERP文獻之結果不同。

Effective rate of protection (ERP) has been widely used in measuring trade protection since Corden (1966). This index has been refined in several ways to adjust for input substitutions, non-traded inputs, exchange rate effects, imperfectly competitive markets, multi-national firms and so on; however, the effects of foreign direct investment (FDI), which is one of the most prevalent issues of the last decade, on ERP have been ignored in the literature. The purpose of this paper is to utilize the ERP definition `a la Anderson (1998) to highlight the impact of FDI on ERP. This paper shows that when FDI is taken into account, the measurement of the ERP no longer monotonically increases along with tariff rates on final goods. This result contradicts conventional wisdom concerning ERP measurement.