本文将新经济地理学中的核心—边缘模型（Core-Periphery model）加以拓展，该模型原本仅考虑由地区间实际工资差异所驱动的工人单向迁移；拓展后新增了由地区间实际利润差异所驱动的企业迁移。在此双重迁移模型中，解的行为在定性上与单迁移模型相似：1）空间上均匀的人口分布变得不稳定，最终形成若干个城市，其中企业与工人共同集聚；2）随着运输成本下降，城市数量减少。这些结果为单迁移模型的应用提供了更一般的理论依据。

The Core-Periphery model in the new economic geography, which considers the single migration of workers driven by real wage inequality among regions, is extended to incorporate the migration of firms driven by real profit inequality among regions. In this dual-migration model, the behavior of solutions is qualitatively similar to that of single-migration models. That is, 1) spatially homogeneous population distributions become destabilized and eventually form several cities where both firms and workers agglomerate; 2) the number of cities decreases as transport costs decrease. These results provide a more general theoretical justification for the use of single migration models.