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 605,918 websites that are Pingdom RUM Customers. We know of 394,681 live websites using Pingdom RUM and an additional 211,237 sites that used Pingdom RUM historically and 327,017 websites in the United States.
Get a list of 605,918 websites using Pingdom RUM which includes location information, hosting data, contact details, 394,681 currently live websites and 211,237 sites that used this technology previously and 327,017 websites in the United States currently using Pingdom RUM.