要旨：This paper revisits the core-periphery model of Krugman (1991) when his CES utility is replaced by a general additively separable sub-utility which captures the income effect and allows variable markups. New evolving paths and bifurcation patterns are created by the interaction between the agglomeration force generated by monopolistic competition, increasing returns to scale, trade cost and the dispersion force resulting from the pro-competitive effect. Autarky does not necessarily produce full dispersion and free trade may not correspond to agglomeration. Moreover, the demand parameter of manufactured goods is crucial to determining the firm location.