產品異質性下之市場規模與廠商的群聚

MARKET SIZE AND AGGLOMERATION IN A SPATIAL COURNOT MODEL OF PRODUCT DIFFERENTIATION

本文在產品異質下探討市場需求規模與廠商之區位選擇關係。我們在線型市場而且消費者均勻分佈的設定下，找出維持廠商群聚於市中心（聚中均衡）的最低市場規模，低於此規模則出現廠商分散的均衡；傳統獲致群聚均衡的結果為本文的特例，乃因所假設之市場需求過大所致。又在非聚中均衡的情況，市場規模越小或同質性越高則兩廠商的設廠地點會相距越遠。

This paper analyzes the relationship between market size and location choice of two firms engaging in quantity competition with differentiated products. Under the model of a linear city with uniformly distributed consumers, we prove that there exists a minimum market size for firms to agglomerate in the market center. On the contrary, the separation equilibrium will occur when market size is below the threshold. Furthermore, we show that the conventional result of central agglomeration equilibrium is indeed a special case of ours, due to its assumption of higher market size than the threshold. We also prove that under separation equilibrium, the smaller the market size and/or the higher the degree of product homogeneity, the larger the separation distance between firms will be.