Before revision:  The proposed PCI, established and demonstrated at the US county level, exhibits a strong positive association with SafeGraph population movement records (10 percent penetration in the US population) and Facebook  social connectedness index (SCI), a popular connectivity index based on social networks.
After revision:  The proposed PCI, established and demonstrated at the US county level, exhibits a strong positive association with SafeGraph population movement records (10 percent penetration in the US population) and Facebook 's social connectedness index (SCI), a popular connectivity index based on social networks.