本文旨在探討廣告的經濟效果，並分析廠商間進行聯合廣告或非合作廣 告、競爭模式（數量競爭或價格競爭）及不同的市場成長性等情況下，對廣告 率及社會福利的影響。文中發現：需求為固定彈性下，若市場具高度成長性， 則數量競爭下廠商間的廣告競爭形態為策略性互補，且相較於價格競爭下有較 高的廣告率。若市場接近飽和，則兩種競爭形態下，廠商間的廣告競爭均為策 略性替代，且價格競爭下有較高的廣告率。高成長性市場中，獨立廣告率低於 最適廣告率，若廠商聯合廣告，則價格競爭下之廣告率將更偏離最適廣告率， 而數量競爭下則可提高廣告率使其接近最適廣告率。反之，若市場已接近飽 和，則非合作均衡之廣告量均過大，此時廠商聯合廣告，不論在何種競爭形態 下，均可降低廣告率並接近最適水準。

ABSTRACT This paper investigates how competitive behavior and market maturity affect the economic effects of advertising. We also compare the effects between the firms’ cooperative and independent advertising. Considering the case of constant elasticity demand function, this paper shows that if the market size can be expanded, the firms’ advertising expenditures in a Cournot model are strategic complements, and the advertising rate is higher than in a Bertrand model. If the industry is mature, no matter what the competition model is, the firms’ advertising expenditures are strategic substitutes and the advertising rate is higher in Bertrand than in Cournot. In an emerging industry, the independent advertising rate is lower than the optimal advertising rate. If firms cooperate in advertising, the advertising rate will deviate from the optimal level in the Bertrand model but will be closer to optimal level in the Cournot Model. In a mature market, on the contrary, the independent advertising rate is higher than the optimal level. If firms cooperate in advertising, the equilibrium advertising rate decreases and will be closer to the optimal level in both competition models.