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 612,458 websites that are Pingdom RUM Customers. We know of 28,733 live websites using Pingdom RUM and an additional 583,725 sites that used Pingdom RUM historically and 17,434 websites in the United States.
Get a list of 612,458 websites using Pingdom RUM which includes location information, hosting data, contact details, 28,733 currently live websites and an additional 496,926 domains that redirect to sites in this list. 583,725 sites that used this technology previously and 17,434 websites in the United States currently using Pingdom RUM.