本論文由三篇論文組成，分別討論貿易保護政策如何影響外國廠商的直接投資誘因、副廠品質提升與原廠生產策略之關係以及原廠自身開放售後服務市場意願。全文以部分均衡理論作為研究基礎，採用倒推求解法計算各章節模型之子賽局完美均衡解。

第二章探討內生市場結構下關稅政策與配額政策對外國廠商FDI決策的影響。我們發現兩家成本對稱的外國廠商在關稅政策(配額政策)下的FDI決策是對稱的(不對稱的)，且廠商在關稅政策下比配額政策下更有可能進行FDI。從國內福利(世界福利)的角度而言，關稅政策下本國福利(世界福利)較配額政策高(低)。最後，若兩家廠商成本不對稱，具有成本優勢的廠商無論在關稅政策或配額政策下皆較有可能進行FDI。

第三章建構一個兩階段之售後服務模型，探討原廠獨占製造商之售後服務部門與副廠維修商間的競爭，以及副廠售後服務品質提升對原廠利潤與社會福利之影響。我們假設前者所提供售後服務品質高於後者，結果顯示副廠的售後服務品質提升對於商品銷售量、原廠利潤及社會福利均存在非線性的關係。副廠售後服務品質提升一方面將會使原廠在售後服務市場更競爭，我們稱之競爭效果；而另一方面則會提升消費者購買商品的意願，我們稱之為商品銷售市場的品質提升效果。在商品之良率低時，競爭效果大於品質提升效果，副廠售後服務品質提升會降低原廠利潤與產出。反之，若商品良率高，則品質提升效果大於競爭效果，副廠售後服務品質提升有利原廠之利潤、產出與社會福利。

第四章採用Hotelling雙佔模型，探討存在售後服務市場時，兩家原廠製造商開放其售後服務市場的誘因。在兩製造商成本對稱下，我們發現在兩家製造商成本對稱下，當廠商較具有商品市場獨佔力時，兩家廠商有誘因開放其商品售後服務市場，但會使消費者剩餘與下降而社會福利不受影響。在生產成本不對稱時，如果商品良率較低，高成本製造商商比低成本製造商有誘因開放其售後服務市場；反之當商品良率較高時，高成本製造商開放其售後服務市場的誘因則較少。在不考慮政府法律規定與存在授權契約等情況下，我們利用理論模型探討擁有商品設計專利權的原廠製造商為什麼有誘因，在不收取授權費用的情況下開放其商品售後服務市場。

This dissertation comprises three papers, each discussing the impact of trade protection policies on foreign firms' incentives for direct investment, the relationship between quality improvement of aftermarket parts suppliers (AMs) and the original equipment manufacturers' (OEM) production strategy, and the willingness of original equipment manufacturers to open the aftermarket service market. The entire work is based on partial equilibrium theory and employs backward induction to compute sub-game perfect equilibrium solutions for each chapter's models.

Chapter 2 investigates the influence of tariff and quota policies on foreign firms' FDI decisions in an endogenous market structure. We find that two cost-symmetric foreign firms' FDI decisions are symmetric (asymmetric) under tariff (quota) policies, and firms are more likely to engage in FDI under tariff policies compared to quota policies. From the perspective of domestic welfare (world welfare), the domestic welfare (world welfare) is higher (lower) under tariff policies than under quota policies. Finally, when the firms' costs are asymmetric, the firm with cost advantages is more likely to engage in FDI under both tariff and quota policies.

In Chapter 3, we construct a two-stage aftermarket service model to examine the competition between the OEM's service sector and the AMs. Additionally, we analyze the impact of AMs' aftermarket service quality improvement on the OEM's profit and social welfare. Assuming that the former provides higher aftermarket service quality than the latter, the results show a nonlinear relationship between AMs' aftermarket service quality improvement and product sales, OEM's profit, and social welfare. The improvement in AMs' aftermarket service quality will enhance competition in the aftermarket service market for the OEM (termed the competition effect) and also increase consumers' willingness to purchase the product (termed the quality improvement effect). When the product's defect rate is low, the competition effect outweighs the quality improvement effect, resulting in a reduction in the OEM's profit and output due to the quality improvement. Conversely, when the product's defect rate is high, the quality improvement effect dominates the competition effect, leading to increased profits, output for the OEM, and social welfare.

Chapter 4 adopts the Hotelling duopoly model to investigate the incentives for two OEMs to open their aftermarket service markets when aftermarket services exist. Under cost symmetry for both manufacturers, we find that when one manufacturer has greater market power in the product market, both manufacturers have an incentive to open their aftermarket service markets, although this would decrease consumer surplus without affecting social welfare. In the case of asymmetric production costs, if the product defect rate is low, the high-cost manufacturer is more likely to open its aftermarket service market than the low-cost manufacturer. Conversely, when the product defect rate is high, the incentive for the high-cost manufacturer to open its aftermarket service market is less. Additionally, in the absence of government regulations or licensing agreements, we utilize the theoretical model to explore why the original equipment manufacturer, holding the product design patent rights, has an incentive to open its product's aftermarket service market without charging licensing fees.

第一章 緒論 1
第二章 市場結構內生化下的貿易保護政策與FDI 5
第三章 產品良率、售後服務競爭與社會福利 27
第四章 產品雙佔下最適售後服務策略 47
第五章 總結 65
附錄 69
參考文獻 73

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