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 626,300 websites that are Pingdom RUM Customers. We know of 82,758 live websites using Pingdom RUM and an additional 543,542 sites that used Pingdom RUM historically and 70,915 websites in the United States.
Get a list of 626,300 websites using Pingdom RUM which includes location information, hosting data, contact details, 82,758 currently live websites and an additional 479,071 domains that redirect to sites in this list. 543,542 sites that used this technology previously and 70,915 websites in the United States currently using Pingdom RUM.