The mechanism for the intra-city employment growth: The role of employment centers

Employment centers serve as crucial drivers of intra-city development, especially in the ubiquitous polycentric transformation. Clarifying the role and impact mechanisms of centers in intra-city growth echoes both theoretical basis and actual needs. However, the empirical understanding is surprisingly limited. Thus, this paper proposes and examines a novel systematical framework with a particular and new focus on the centers' influence. Instead of focusing only on developed regions, both areas outside centers and two types of sub-centers are investigated in this research. The empirical results using Shanghai as a study case show that the effects of agglomeration of centers are mostly insignificant on average but conditioned by three types of proximities to centers. Geographic proximity strengthens the positive role of agglomeration of centers on areas outside centers within the city and developing sub-centers within a certain distance to main-center, but intensifies the siphonic effects for the case of stabilized sub-centers. The industrial proximity only positively moderates the effect of agglomeration of centers on developing sub-centers, while the moderating role of proximity of agglomeration scale to main-center is significantly negative in all areas. These discoveries provide valuable insights for urban spatial and development planning, especially in polycentric cities.