Each at its Own Pace: Third-Party Dependency and Centralization Around the World

We describe the results of a large-scale study of third-party dependencies around the world based on regional top-500 popular websites accessed from vantage points in 50 countries, together covering all inhabited continents. This broad perspective shows that dependencies on a third-party DNS, CDN or CA provider vary widely around the world, ranging from 19% to as much as 76% of websites, across all countries. The critical dependencies of websites -- where the site depends on a single third-party provider -- are equally spread ranging from 5% to 60% (CDN in Costa Rica and DNS in China, respectively). Interestingly, despite this high variability, our results suggest a highly concentrated market of third-party providers: three providers across all countries serve an average of 92% and Google, by itself, serves an average of 70% of the surveyed websites. Even more concerning, these differences persist a year later with increasing dependencies, particularly for DNS and CDNs. We briefly explore various factors that may help explain the differences and similarities in degrees of third-party dependency across countries, including economic conditions, Internet development, economic trading partners, categories, home countries, and traffic skewness of the country's top-500 sites.