本文以Symeonidis (2003)的經濟模型架構為基礎，考量一雙佔市場，產品具水平差異和垂直差異下，廠商可通過產品研發來提升自身產品的品質。在兩廠商具對稱性性質下，廠商進行兩階段的賽局博弈，第一階段廠商同時決定其研發投入，第二階段廠商同時決定產量或價格。經過分析，我們可得以下幾個重要之結果：(i) 獨佔廠商的產品研發投入為最高。(ii) 數量競爭相較於價格競爭，廠商的產品研發投入更多。(iii) 在價格競爭下，廠商研發投入與廠商間的競爭程度呈負相關。在數量競爭中卻不一定。(iv) 價格競爭相較於數量競爭模式下，因廠商間的競爭更激烈，故產量較高價格較低、消費者福利較高、廠商利潤較低、且社會總福利較高。(v) 數量競爭下產品間的可替代性與消費者福利呈負相關，價格競爭下產品間的可替代性與消費者福利呈正相關。(vi) 兩種不同競爭方式下的市場總福利與產品間的可替代性呈負相關。

In this paper, we find that in the duopoly market, firms can enhance the quality of product through product R&D and the product have horizontal and vertical differences on the basis of Symeonidis (2003) economic model structure. In case of two firms with symmetric property, there will have two-stage game. The firms will decide their product R&D simultaneously in the first stage and decide the quantity or price in the second stage. It is shown that: (i) the monopoly firms have the highest input in product R&D.(ii) The R&D input in the Cournot competition is more than in the Bertrand competition. (iii) In the Bertrand competition, the firm’s R&D input is negatively correlated with their competition level but in Cournot competition is not necessarily.(iv) Since the firms in Bertrand competition is even more competitive in the quantity competition, so the quantity, consumer surplus and total social welfare is higher but lower in price and profit.(v) The inverse measure of the degree of horizontal product differentiation is negatively correlated with the consumer surplus in the quantity competition but positively correlated in price competition.(vi) The social total welfare and inverse measure of the degree of horizontal product differentiation have a negative correlation in both Cournot and Bertrand competition .

目錄
摘要....................................1
Abstract................................2
致謝....................................3
目錄....................................4
圖目錄..................................7
第一章 論文介紹.........................10
1.1 研究背景與動機......................10
1.2 研究目的...........................10
第二章 文獻回顧.........................11
第三章 經濟模型構建.....................12
3.1消費者效用函數.......................12
3.2反需求和需求函數......................12
3.3 賽局的順序...........................13
3.4第二階段: 數量 (Cournot) 競爭下均衡....13
3.5 第二階段: 價格 (Bertrand) 競爭下均衡..14
3.6 第一階段:廠商i選擇 ui.................15
第四章 數量競爭下均衡分析..................15
4.1 均衡研發投入..........................15
4.2 均衡產量和價格........................17
4.3 均衡總利潤............................17
4.4 消費者福利............................17
4.5 社會總福利............................18
第五章 價格競爭下均衡分析..................18
5.1 均衡研發投入..........................18
5.2 均衡產量和價格........................20
5.3 均衡總利潤............................21
5.4 消費者福利............................22
5.5 社會總福利............................22
第六章 數量競爭與價格競爭下均衡之比較分析....23
6.1 研發投入..............................23
6.2 均衡產量和價格.........................24
6.3 總利潤................................24
6.4 消費者福利............................24
6.5 社會總福利............................24
第七章 數量競爭與價格競爭下均衡之比較靜態分析..25
7.1 研發投入..............................25
7.2 數量競爭下均衡產量.....................26
7.3 價格競爭下均衡價格.....................26
7.4 總利潤................................27
7.5 消費者福利............................27
7.6 社會總福利............................28
第八章 結論...............................29
附錄.....................................31
附錄一...................................31
附錄二...................................31
附錄三...................................32
附錄四...................................32
附錄五...................................33
附錄六...................................33
附錄七...................................34
附錄八...................................36
附錄九...................................36
附錄十...................................40
附錄十一.................................44
參考文獻.................................50

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