The Center's Web Privacy Census, conduced each year, crawled the most-trafficked sites on October 24, measuring the number of first-party and third-party cookies spotted on the top 100, top 1,000 and top 25,000 sites. In addition to checking website home pages, which it calls a "shallow crawl," the census project conducted "deep crawls," checking up to six random links on the same sites.
The privacy census measured the top sites as reported by Quantcast. According to the Quantcast site, the top 10 U.S. sites are Google, YouTube, Facebook, MSN, Twitter, Yahoo, Amazon, Wikipedia, Microsoft.com and Huffington Post. Others in the top 100 include Weather.com, eBay, ToysRUs.com, Walmart.com, IMDB, WebMD, Politico, Flickr, BuzzFeed, BarackObama.com and Time.com."