Human Settlement Quality Evaluation Based on Air Quality in Major Cities of China

Table 3

Coupling degree classification and coupling level of the human settlements system.

Coupling values	Coupling stage	Coupling characteristics
0 < C ≤ 0.3	Low-level coupling	Primary development of socioeconomic and infrastructure; poor natural environment carrying capacity
0.3 < C ≤ 0.5	Antagonistic coupling	Rapid development of social and economy; the increasing contradiction between the natural environment and human society
0.5 < C ≤ 0.8	Run-in phase	A benign coupling stage of systems
0.8 < C ≤ 1	High-level coupling	Mutual promotion and development among systems