Table 1 Definition of Variables and Their Sources.
Index | Variable Name | Definition | average | statistics | min | max |
|---|---|---|---|---|---|---|
Dependent Variable | Flow | Total annual intercity contacts (in numbers of people) | 25,377.73 | 82,548.89 | 2.00 | 2,014,300.00 |
Geographical Factors | Distance | Distance between city centers (km) | 998.62 | 654.54 | 17.16 | 3,782.35 |
Population Factors | o_pop/d_pop | City population (in thousands) - measuring population scale | 5,949.80 | 5,053.41 | 210.00 | 33,900.00 |
Economic Factors | o_gdp/d_gdp | City GDP (in million of yuan) - measuring economic scale | 592,851.66 | 725,837.92 | 21,000.00 | 3,100,000.00 |
o_expend/d_expend | City fiscal expenditure (in million of yuan) - measuring public service level | 100,326.24 | 149,203.76 | 2,772.74 | 750,000.00 | |
o_sci/d_sci | City science expenditure (in million of yuan) - measuring public service level | 3,987.68 | 8,521.13 | 9.73 | 39,000.00 | |
o_indus/d_indus | Proportion of secondary industry in the city - measuring industrial structure | 41.58 | 11.12 | 4.00 | 71.34 | |
o_edu/d_edu | City education expenditure (in million of yuan) - measuring public service level | 14,984.70 | 19,309.91 | 412.49 | 96,000.00 | |
Environmental Factors | o_aqi/d_aqi | City’s average annual air quality - measuring environmental quality | 69.97 | 18.53 | 33.45 | 114.12 |
o_pm25/d_pm25 | City’s average annual pm2.5 - measuring environmental quality | 39.52 | 12.37 | 14.14 | 72.36 |
