Table 2.

Descriptive statistics of subregion pairs

	Mean	SD	N
Migration ($M_{\mathit{ij}}$)	9.52	57.84	30,450
$log{M}_{\mathit{ij}}$	0.59	0.58	18,945
N. of connections (${\text{SC}}_{\mathit{ij}}^{\text{brid}}$)	9688	66,457	30,450
log ${\text{SC}}_{\mathit{ij}}^{\text{brid}}$	3.05	0.77	30,450
Driving distance in minutes ($D_{\mathit{ij}}$)	176.61	77.93	30,448
$log{D}_{\mathit{ij}}$	2.19	0.23	30,448
Driving distance weighted by migration	85.80	61.04	18,943

log transformations are 10-based