From the webpage:
During our January 2016 measurement of the top 1 million sites, our tool made over 90 million requests, assembling the largest dataset (to our knowledge) used for studying web tracking. With this scale we can answer many web tracking questions: Who are the largest trackers? Which sites embed the largest number of trackers? Which tracking technologies are used, and who is using them? and many more.
The total number of third parties present on at least two first parties is over 81,000, but the prevalence quickly drops off. Only 123 of these 81,000 are present on more than 1% of sites. This suggests that the number of third parties that a regular user will encounter on a daily basis is relatively small. The effect is accentuated when we consider that different third parties may be owned by the same entity. All of the top 5 third parties, as well as 12 of the top 20, are Google-owned domains. In fact, Google, Facebook, and Twitter are the only third-party entities present on more than 10% of sites.
… (emphasis in original)
Impressive research based upon an impressive tool, OpenWPM.
The Github page for OpenWPM reads in part:
OpenWPM is a web privacy measurement framework which makes it easy to collect data for privacy studies on a scale of thousands to millions of site. OpenWPM is built on top of Firefox, with automation provided by Selenium. It includes several hooks for data collection, including a proxy, a Firefox extension, and access to Flash cookies. Check out the instrumentation section below for more details.
Just a point of view but I’m more interested in specific privacy tracking data for some given set of servers than general privacy statistics.
Specific privacy tracking data that enables planning the use of remote browsers to leave false trails.
Kudos to the project, however you choose to use the software.