Fig. 7

Wilcoxon rank-sum tests for the metric values across three different county groups. The metrics are: a weekly new cases (first-order growth rate) over the week from March 17 to March 24; b population size; c co-location degree centrality over the week March 31; and d the percentage reduction of the co-location probability for different types of links over the week from March 10 to March 17. HH means the edges connecting two counties both from the high-risk group; HM means the edges connecting one county from high risk group and another county from medium risk group, and so on so forth. (The ranks based on the data in different weeks were performed as a sensitivity test provided in Additional file 1). Note: *** p < 0.01; ** p < 0.05; * p < 0.1