Fig 1.
Schematic diagram of “dot-like” structures.
Fig 2.
Schematic diagram of “axial” structures.
Fig 3.
Schematic diagram of “network” structures.
Fig 4.
Schematic diagram of “planar” structures.
Fig 5.
China’s five-level administrative management system.
Fig 6.
The hierarchical system of Chinese cities.
Fig 7.
Schematic diagram of a “tiered” structure.
Fig 8.
Diagram of concentric urban agglomeration spatial mechanism (before).
Fig 9.
Diagram of concentric urban agglomeration spatial mechanism (after).
Fig 10.
Theoretical mechanism diagram.
Fig 11.
Research area. Note: The vector data for China's administrative boundaries were obtained from the Standard Map Service website of the Ministry of Natural Resources of China (http://211.159.153.75/index.html).
Fig 12.
RES of Chinese urban agglomerations.
Fig 13.
POP of Chinese urban agglomerations.
Fig 14.
ENT of Chinese urban agglomerations.
Fig 15.
GAP of Chinese urban agglomerations.
Fig 16.
GRAD of Chinese urban agglomerations. Note: The vector data for China's administrative boundaries were obtained from the Standard Map Service website of the Ministry of Natural Resources of China (http://211.159.153.75/index.html).
Table 1.
Descriptive statistics of variables (2005–2019).
Table 2.
Main regression and robustness results.
Table 3.
Threshold effect significance test.
Table 4.
Threshold regression results.
Table 5.
Heterogeneity regression results by coastal status.
Table 6.
Heterogeneous regression results based on the inclusion of national central cities.