Comscore estimates that Facebook’s monthly audience has more than doubled from 54.5 million U.S. unique visitors to 112 million unique visitors during December 2009. That makes it the fourth-most popular U.S. Web property — behind only those of Google, Yahoo and Microsoft.
Unique visitors, page views, and total time spent all doubled as well. At the same time, frequency metrics such as average minutes per day (up 6% to 23.7) and average usage days per visitors (up 37% to 10.4) also increased.
The only key category where Facebook has dropped off this year is in average minutes per visit, down 11% to nine minutes. That’s to be expected as a result of users visiting the site more frequently. So people are making more but shorter visits. Average monthly minutes per visitor increased 45% from 170 to 247.
