Table 1 Definition of the variables.

I (carbon emission, 10³ ton)

19,272.23

22,510.06

95.6

77,934.1

si (specialized agglomeration, %)

1.049

0.486

0.221

1.865

di (diversified agglomeration, %))

0.3030

0.2865

0.1075

1.349

po (population size in districts, people)

3,037,872

3,175,695

122,153

1.30e+07

pergdp (GDP per capita, won/person)

3.49e+07

1.07e+07

1.90e+07

6.50e+07

edu (the proportion of Bachelor, Master and PhD graduates, %)

0.009

0.004

0.003

0.024

secondrate (the proportion of secondary industry employment, %)

0.398

0.072

0.222

0.588

tecgdp (technological innovation, R&D costs/GDP, %)

0.035

0.041

0.007

0.193

fdi (foreign direct investment, 10⁶ dollar)

789.9751

1621.377

0

8339