Real User Monitoring gives insight into performance for actual users visiting the website.
https://www.pingdom.com/rum/
Analytics and Tracking · Application Performance
Get access to data on 615,693 websites that are Pingdom RUM Customers. We know of 30,602 live websites using Pingdom RUM and an additional 585,091 sites that used Pingdom RUM historically and 19,011 websites in the United States.
Get a list of 615,693 websites using Pingdom RUM which includes location information, hosting data, contact details, 30,602 currently live websites and an additional 490,029 domains that redirect to sites in this list. 585,091 sites that used this technology previously and 19,011 websites in the United States currently using Pingdom RUM.