There are far more people on Facebook than live in the United States. On July 21, Facebook announced it had reached a milestone: signing up its 500 millionth user. In addition to adding more than a half billion users in the six years since its launch, Facebook is also now the most-visited site on the Internet. Zuckerberg wrote of the milestone on his blog: "I could have never imagined all of the ways people would use Facebook when we were getting started six years ago. I want to thank you for being part of making Facebook what it is today and for spreading it around the world." Today, more than 70% of users live outside the U.S.