本文將理論建立於新國貿理論之寡佔市場上，並引入所有權之因素，以探討外國 廠商握有本國廠商之所有權對本國國內市場開放程度之影響， 並以美國在 1977 年到 1990 年間 19 大製造業之資料作實證分析。在實證中，本文採用兩種不同標準以衡量外人所有權 之持有: 一為資產衡量法，一為產值衡量法。無論採用何種標準，其實證結果均與理論所預 期者一致，亦即外人握有美國廠商之所有權對美國產業之國內市場開放程度 (以進口值佔國 內需求比率衡量 ) 有顯著性之負面影響。 又當美國國內之潛在市場規模擴大或市場結構愈 趨壟斷時，美國產業之國內市場開放程度有明顯提高之趨勢。而貿易障礙對美國產業之國內 市場開放程度之影響，則視障礙種類不同與所有權之衡量方法而定，若所有權以資產衡量法 為標準，則關稅與運輸成本對美國產業之國內市場開放程度有顯著之負面影響，而非關稅障 礙之影響雖仍為負，但效果不顯著; 若所有權以產值衡量法為標準，則只有運輸成本對美國 之國內市場開放程度有顯著性之負面影響，而關稅與非關稅障礙之影響則不顯著。最後，衡 量產品差異化程度之廣告支出密集度對美國產業之國內市場開放程度有正面影響，但統計上 不顯著。

　　　　　This paper theoretically and empirically develops a model based on the new trade theory to examine how foreign ownership affects the openness in the domestic market. The US manufacturing data between 1977 and 1990 are used for the empirical work. Foreign ownership is measured by two approaches: asset approach and sales approach. The empirical results in both approaches are consistent with what the theoretical model predicts. The results show that as the share of the foreign ownership in the US increases, the openness in the US domestic market decreases. Both monopoly power and the potential market size in the US domestic market have positive effects on the openness in the US domestic market. The effects of trade barriers depend on the types of trade barriers and the measurement approach for foreign ownership. If the measurement is based on the asset approach, both tariffs and transportation costs have significantly negative effects; however, the effects of nontariff barriers are insignificantly negative. If the sales approach is utilized, only transportation costs have significantly negative effects. Both effects of tariffs and nontariff barriers are insignificant. Finally, the product differentiation measured by the intensity of advertising has positive but insignificant effects on the openness in the US domestic market.